Hi,
I'm designing architecture of a text parser. Example sentence: Content here, content here.
Whole sentence is a... sentence, that's obvious. The, quick etc are words; , and  . are punctuation marks. But what are words and punctuation marks all together  in general? Are they just symbols? I simply don't know how to name what a single sentence consists of in the most reasonable abstract way (because one may write it consists of letters/vowels etc).
Thanks for any help :)