What is the difference among many "if" words? In Mandarin, there are too many words to express "if". Here is a brief list of such words, as far as I recall:


如果
如
假如
只要
即便
要说


Some words such as 尽管 have different meanings, such as "although". In these cases I understand the difference. 

But if these words just mean "if" in English, is there any difference on the usage and context where some of these words are appropriate while others are not?
如果: simply means 'if'. For example, 如果我知道，我就会告诉你。 If I knew it, I    would tell you.
  如： is short for 例如, meaning 'for example', 'like' or 'as'. It's used    when you give some examples. For example (如)： 手字可以和很多字组词，如：手机.
  假如: supposing or in case. For example: 假如生活欺骗了你, in case/supposing    life deceived you.
  只要: only if or as long as. For example: 只要你做完工作就可以走了。You could go as long as you finish the work.
  即便: even if/even though. For example: 即便是老板，我也不怕。 Even though he is    the boss, I wouldn't fear.
  要说: as for; want to say something; For example, 要说他这个人，没人知道。As for    this person, no one knows. 我没有什么要说。 There is nothing I want to say.