Language Notes

* grammatical number
"Number" is the singularity or plurality of a noun or verb or what have you. Today, in English, we only have two categories of grammatical number, singular and plural. There used to be a third category, called "dual," which was used to indicate the "twoness" of something. Hence, there were pronouns not only for "I" and "we" but also "we two". This feature has dropped out of most Indo-European languages, but is apparently present in modern Arabic.

* Chinese "we"
Chinese has two pronouns both used to express we: (1) The "we" that includes the listener (and possibly others) and (2) the "we" that includes the speaker and one or more others, but not the listener. Thus:

(1) John, it's great that you and I both liked that movie we just saw.

(2) John, my husband and I saw a movie last night. We recommend it!
This is a great example of how some conceptual distinctions are given more weight in some languages than in others; of how some meaning is implicit and some is explicit; of the role of context in communication.

Source:
http://www.cs.princeton.edu/~aahobor/Lucy-Day/About-Me/Language-Notes.shtml