question: Why are some words across different languages very similar while most are hugely different?
comment: When the word for something is similar in two (or more) languages, it usually means that it has the same origin. For instance, romance languages like French and Spanish have Latin origins, so there is a lot of overlap in their vocabulary, albeit with slight variations in spelling/pronunciation. Additionally, similarities across languages can come from the history of the people who speak it. Persian Farsi is not an Arabic language, although it is written in Arabic script (with some variations) and uses a TON of Arabic words. This is because of the Muslim conquest of Persia way back when. Persians were forced to adopt Arabic, though they fought back and maintained their own language (for the most part). Finally, another reason for similar-sounding words can be that one language may not have a word for something. “Computer,” for example. Computers are relatively new thing, and instead of coming up with their own, unique-sounding word for “computer,” many languages simply adopted a similar-sounding word. These are called cognates. Fun fact relating to to cognates: Iran actually has a committee in place that is dedicated to creating new, purely Persian words to replace cognates and Arabic words. At least, that’s what one of my teachers told me.
passages: The shared features of languages which belong to the same typological class type may have arisen completely independently. Their co-occurrence might be due to universal laws governing the structure of natural languages, "language universals", or they might be the result of languages evolving convergent solutions to the recurring communicative problems that humans use language to solve.
  
  Section::::Social contexts of use and transmission.
   Latin is usually the most common source of loanwords in these languages, such as in Italian, Spanish, French, etc., and in some cases the total number of loans may even outnumber inherited terms (although the learned borrowings are less often used in common speech, with the most common vocabulary being of inherited, orally transmitted origin from Vulgar Latin). This has led to many cases of etymological doublets in these languages.
   The classification of languages into language families begins by making a list of words in the potential languages that exhibit lexical and grammatical similarities; that is, they are similar in sound and meaning. The next step is to determine how the similarities originated. There are three possibilities: convergence, borrowing and common origin. Convergence is the chance similarity of sound and meaning of a word in two different languages and "is based on the principle that a word is an arbitrary association of sound and meaning". An example of convergence is that many unrelated languages have words similar to "mama" and "papa" for 'mother' and 'father'. Borrowing results from the exchanging of words between languages in close contact with one another. Once convergence and borrowing have been eliminated as possible explanations for similarities in sound and meaning of words, the last explanation is common origin. It can be assumed that the similarities occurred due to descent from a common ancestor, and the words are known as cognates. The set of all cognates of a word is the etymology of the word.
   Redundancy, and "useless" or "nonsensical" words (or phrases, or morphemes), can also be inherited by one language from the influence of another and are not pleonasms in the more critical sense but actual changes in grammatical construction considered to be required for "proper" usage in the language or dialect in question. Irish English, for example, is prone to a number of constructions that non-Irish speakers find strange and sometimes directly confusing or silly:
   The lexical similarity is only one indication of the mutual intelligibility of the two languages, since the latter also depends on the degree of phonetical, morphological, and syntactical similarity. The variations due to differing wordlists weigh on this. For example, lexical similarity between French and English is considerable in lexical fields relating to culture, whereas their similarity is smaller as far as basic (function) words are concerned. Unlike mutual intelligibility, lexical similarity can only be symmetrical.
  
  Section::::Indo-European languages.
   The influence can go deeper, extending to the exchange of even basic characteristics of a language such as morphology and grammar. Nepal Bhasa, for example, spoken in Nepal, is a Sino-Tibetan language distantly related to Chinese but has had so many centuries of contact with neighbouring Indo-Iranian languages that it has even developed noun inflection, a trait that is typical of the Indo-European family but rare in Sino-Tibetan. It has absorbed features of grammar as well such as verb tenses. Romanian was influenced by the Slavic languages spoken by neighbouring tribes in the centuries after the fall of the Roman Empire not only in vocabulary but also in phonology and morphology. English has a few phrases, adapted from French, in which the adjective follows the noun: court-martial, attorney-general, Lake Superior. It is easy to see how a word can diffuse from one language to another, but it is not as obvious how more basic features can do the same even if the latter phenomenon is not rare.
   Besides systematic changes, languages are also subject to random mutations (such as borrowings from other languages, irregular inflections, compounding, and abbreviation) that affect one word at a time, or small subsets of words. For example, Spanish "perro" (dog), which does not come from Latin, cannot be rule-mapped to its Italian equivalent "cane" (the Spanish word "can" is the Latin-derived equivalent but is much less used in everyday conversations, being reserved for more formal purposes). As those sporadic changes accumulate, they will increasingly obscure the systematic ones—just as enough dirt and scratches on a photograph will eventually make the face unrecognizable.
   Languages are all hybrid, in varying degrees. For centuries people borrowed from foreign languages, creating thus hybrid linguistic idioms. They did so for commercial, aesthetic, ideological and technological reasons (to facilitate trade transactions, express philosophical or scientific ideas unavailable in their original idioms, enrich and adapt their languages to new realities, subvert a dominant colonial literary canon by deliberately introducing words from the colonized peoples' idiom). Trade and colonization have been the main vehicles of linguistic hybridization across history. Since the classical conquests, both the colonizers and colonized tapped into each other's languages. The Greeks soaked up many mathematical and astronomical concepts from the Egyptians. The Romans, too, absorbed much of Greek culture and ideas. They also drew abundantly from the "barbarians". In "Taktika", Arrian (92–175 AD), a Greek historian and philosopher of the Roman period, drew attention to the Romans' indebtedness to their colonial subjects, arguing that "the Romans have many foreign (Iberian, Celtic) terms for formations, for they used Celtic cavalry". In modern times, the French and British resorted to similar linguistic appropriations throughout their conquests. The French language, for example, contains over 200 Arabic and Berber words, most of which were taken up during France's colonization of Algeria. Similarly, hundreds of Indian words entered the English idiom from the seventeenth to the nineteenth century. According to "The Oxford English Dictionary," 900 English words are of Indian origin. Linguistic hybridity was manifest in these colonial contexts, but was acknowledged by neither the colonizers nor the colonized. More still, while these linguistic borrowings had, de facto, rendered colonial languages hybrid and therefore impure, the myth of linguistic purity and superiority, inherited from the ancient Greeks’ "linguistic racialism", held firmly among the European colonizers. The Greek word ‘barbarian,’ which was used to refer to non-Greek languages’ inferiority, backwardness and inarticulacy, was adopted by the French since the 16th century. It was often applied to the Basque, Breton and Occitan languages and to their speakers. Abbé Grégoire recommended wiping out these "crude idioms" and forcing French on the Basques, Bretons and Occitans to "spread enlightened ideas (...), well-being and political tranquillity". According to him, this would "banish superstition" and "simplify the mechanism of the political machine." It would, above all, "mould the citizens into a national whole" In Britain, this Aristotelian view of language was revitalized by authors like Jonathan Swift, Samuel Johnson, and Matthew Arnold, who cast respectively the Irish, Scots and Welsh as "rude" and "backward", attributing these peoples’ intellectual and economic "backwardness" to their "inferior" languages.
   Section::::Cultural aspects.
  
  According to Hans Henrich Hock and Brian Joseph, "languages and dialects ... do not exist in a vacuum": there is always linguistic contact between groups. The contact influences what loanwords are integrated into the lexicon and which certain words are chosen over others.
  
  Section::::Leaps in meaning.
   False cognates are pairs of words that seem to be cognates because of similar sounds and meaning, but have different etymologies; they can be within the same language or from different languages, even within the same family. For example, the English word "dog" and the Mbabaram word "dog" have exactly the same meaning and very similar pronunciations, but by complete coincidence. Likewise, English "much" and Spanish "mucho" which came by their similar meanings via completely different Proto-Indo-European roots. This is different from false friends, which are similar-sounding words with different meanings, but which may in fact be etymologically related. (For example: Spanish "dependiente" looks like "dependent", but means sales assistant or clerk as well.)
   Languages differ widely in how much they rely on morphological processes of word formation. In some languages, for example, Chinese, there are no morphological processes, and all grammatical information is encoded syntactically by forming strings of single words. This type of morpho-syntax is often called isolating, or analytic, because there is almost a full correspondence between a single word and a single aspect of meaning. Most languages have words consisting of several morphemes, but they vary in the degree to which morphemes are discrete units. In many languages, notably in most Indo-European languages, single morphemes may have several distinct meanings that cannot be analyzed into smaller segments. For example, in Latin, the word "bonus", or "good", consists of the root "bon-", meaning "good", and the suffix -"us", which indicates masculine gender, singular number, and nominative case. These languages are called "fusional languages", because several meanings may be fused into a single morpheme. The opposite of fusional languages are agglutinative languages which construct words by stringing morphemes together in chains, but with each morpheme as a discrete semantic unit. An example of such a language is Turkish, where for example, the word "evlerinizden", or "from your houses", consists of the morphemes, "ev-ler-iniz-den" with the meanings "house-plural-your-from". The languages that rely on morphology to the greatest extent are traditionally called polysynthetic languages. They may express the equivalent of an entire English sentence in a single word. For example, in Persian the single word "nafahmidamesh" means "I didn't understand it" consisting of morphemes "na-fahm-id-am-esh" with the meanings, "negation.understand.past.I.it". As another example with more complexity, in the Yupik word "tuntussuqatarniksatengqiggtuq", which means "He had not yet said again that he was going to hunt reindeer", the word consists of the morphemes "tuntu-ssur-qatar-ni-ksaite-ngqiggte-uq" with the meanings, "reindeer-hunt-future-say-negation-again-third.person.singular.indicative", and except for the morpheme "tuntu" ("reindeer") none of the other morphemes can appear in isolation.
   Many linguists reject the methods used to determine these forms. Several areas of criticism are raised with the methods Ruhlen and Gell-Mann employ. The essential basis of these criticisms is that the words being compared do not show common ancestry; the reasons for this vary. One is onomatopoeia: for example, the suggested root for 'smell' listed above, *"čuna", may simply be a result of many languages employing an onomatopoeic word that sounds like sniffing, snuffling, or smelling. Another is the taboo quality of certain words. Lyle Campbell points out that many established proto-languages do not contain an equivalent word for *"putV" 'vulva' because of how often such taboo words are replaced in the lexicon, and notes that it "strains credibility to imagine" that a proto-World form of such a word would survive in many languages.
   However, many groups of languages are partly mutually intelligible, i.e. most speakers of one language find it relatively easy to achieve some degree of understanding in the related language(s). Often the languages are genetically related, and they are likely to be similar to each other in grammar, vocabulary, pronunciation, or other features.
   Section::::Numbers of phonemes in different languages.
  
  All known languages use only a small subset of the many possible sounds that the human speech organs can produce, and, because of allophony, the number of distinct phonemes will generally be smaller than the number of identifiably different sounds. Different languages vary considerably in the number of phonemes they have in their systems (although apparent variation may sometimes result from the different approaches taken by the linguists doing the analysis). The total phonemic inventory in languages varies from as few as 11 in Rotokas and Pirahã to as many as 141 in !Xũ.
   There are many examples of words borrowed from foreign languages, and subsequently changed by folk etymology.
   The adoption of words and names from one language to another is also a process that has been going on since time immemorial, although it causes problems in that the phonology of the source language is almost certainly going to be different from that in the destination language, and so mutation of the pronunciation is inevitable. This is perhaps even more of a thorny issue than the above examples of change within a language, because of the possibility that speakers of the source language may be upset at what they may see as the mangling of their language.
   For instance, one could demonstrate that Spanish is related to Italian by showing that many words of the former can be mapped to corresponding words of the latter by a relatively small set of replacement rules—such as the correspondence of initial "es-" and "s-", final "-os" and "-i", etc. Many similar correspondences exist between the grammars of the two languages. Since those systematic correspondences are extremely unlikely to be random coincidences, the most likely explanation by far is that the two languages have evolved from a single ancestral tongue (Latin, in this case).
   A characteristic of Sambahsa is to include words found in different language families, while the most famous auxiliary languages tend to limit themselves to a compilation of Romance vocabulary with some borrowings from the Germanic languages. For example:
  
  BULLET::::- "schkaf" (cupboard) has cognates both in Germanic and Slavic languages: Russian , Polish , Ukrainian , Danish , Icelandic , Franconian dialect and Swedish .
   The most common method applied in pseudoscientific language comparisons is to search two or more languages for words that seem similar in their sound and meaning. While similarities of this kind often seem convincing to laypersons, linguistic scientists consider this kind of comparison to be unreliable for two primary reasons. First, the method applied is not well-defined: the criterion of similarity is subjective and thus not subject to verification or falsification, which is contrary to the principles of the scientific method. Second, the large size of all languages' vocabulary and a relatively limited inventory of articulated sounds used by most languages makes it easy to find coincidentally similar words between languages.
   All languages borrow words from other languages in various contexts. They are likely to have followed the laws of the languages from which they were borrowed rather than the laws of the borrowing language. Therefore, studying borrowed words will probably mislead the investigator, since they reflect the customs of the donor language, the language which is the source of the word.
  
  Section::::Limitations.:Problems with the neogrammarian hypothesis.:Areal diffusion.
   Because cognate words play an important role in mutual intelligibility between languages, these figure prominently in such analyses. The higher the percentage of cognate (as opposed to non-cognate) words in the two languages with respect to one another, the lower is their linguistic distance. Also, the greater the degree of grammatical relatedness (i.e. the cognates mean roughly similar things) and lexical relatedness (i.e. the cognates are easily discernible as related words), the lower is the linguistic distance. As an example of this, the Hindustani word "pānch" is grammatically identical and lexically similar (but non-identical) to its cognate Punjabi and Persian word "panj" as well as to the lexically dissimilar but still grammatically identical Greek "pent-" and English "five". As another example, the English "dish" and German "tisch" 'table' are lexically (phonologically) similar but grammatically (semantically) dissimilar. Cognates in related languages can even be identical in form, but semantically distinct, such as "caldo" and "largo", which mean respectively 'hot' and 'wide' in Italian but 'broth, soup' and 'long' in Spanish. Using a statistical approach (called lexicostatistics) by comparing each language's mass of words, distances can be calculated between them. In technical terms, what is calculated is the Levenshtein distance. Based on this, one study compared both Afrikaans and West Frisian with Dutch to see which was closer to Dutch. It determined that the Dutch and Afrikaans (mutual distance of 20.9%) were considerably closer than Dutch and West Frisian (mutual distance of 34.2%).
   In Belgium, similarities between Dutch and French words often lead to confusion when several different meanings of the same word are mixed up and thus mistranslated. In satirical sketch comedy "Sois Belge et tais-toi!", performed by Joël Riguelle in 2009, the following examples are given: 
  
  The Italian word "confetti" (sugared almonds) has acquired a new meaning in English, French and Dutch; in Italian, the corresponding word is "coriandoli".
  
  English and Spanish, both of which have borrowed from Greek and Latin, have multiple false friends.
   English and Japanese also have diverse false friends, many of them being "wasei-eigo" and "gairaigo" words.
  
  Section::::Causes.:Homonyms.
   "Words are not synonyms on their own. What happens is, that we, speaking the same language, “match make them” every day... You never look for a word by locating it as a vector diagram in a system theory... The latest edition of Encyclopædia Britannica does not even waste space for synonyms... The ambition to locate the appropriate word for the correct use of language is sought no more..."
   Cross-linguistic onomatopoeias
  
  Because of the nature of onomatopoeia, there are many words which show a similar pronunciation in the languages of the world. The following is a list of some conventional examples:
  
  Section::::Collisions, bursts, and strikes.
  
  Section::::Collisions, bursts, and strikes.:Balloon or bubble bursting.
  
  BULLET::::- In Albanian, "pau, puf"
  
  BULLET::::- In Arabic, "pakh, poof"
  
  BULLET::::- In batak. "tak"
  
  BULLET::::- In Bemba, "pobo"
  
  BULLET::::- In Bengali, "phat, phatash"
  
  BULLET::::- In Bulgarian, "puc" пук, "pa" па
  
  BULLET::::- In Croatian, "puk"
  
  BULLET::::- In Czech, "puf"
  
  BULLET::::- In Danish, "bang", "knald"
  
  BULLET::::- In Dutch, "pang", "pof", "paf"
  
  BULLET::::- In English, "pop", "bang"
  