written characters: yuē vs rì I have some troubles in distinguishing written characters 曰 yuē (to speak) and 日 rì (sun). Although they singularly look different on computers (maybe yuē look a bit wider, while rì is taller), I find it almost impossible to distinguish them when they appear in composite characters, or even alone in handwritten texts. Is there some difference I cannot catch that I should pay attention to? Do their writing differ in stroke order?
Thanks!

As pointed out in some answers and comments, there are other sets of characters that look very similar. Among them: 口 kǒu​ (mouth) and 囗 wéi​ (enclosure); 人 rén (person) and 入 rù (to enter), 千 qiān (thousand) and 干 gān (stem), 已    yǐ (stop) and 己 jǐ (self)
I was secretly expecting this question. :)

In handwritten and calligraphic realization, these characters can be tough to distinguish, although the context will help you a lot.

In printed text, the middle 横 héng stroke in 曰 is not touching the right side of the character, in 日 the middle stroke is entirely through, at least in most fonts. If not, it is only the width of the character that can give you a clue and the context, of course.

Needless to say, 曰 is not very common today, it is mostly used in Confucian text, like 子曰, "The Master said...". So most of the time you see these characters in modern texts, chances are it is 日 and not 曰.  

The stroke order is the same.