The subject of every sentence is either SINGULAR (= one) or PLURAL (= two or more).
The subject of a sentence is always one of these (with examples):
The subject can be one word or more than one word.
With 3rd person, it is important to know if the subject is singular or plural because the form of the verb is sometimes different (Lesson 4). Only one word of the subject tells you the answer. For example:
one in "one of my friends" is singular.
problems in "money problems" is plural.
subjects with and are plural.
NOTICE: We use I, you, we, they for both men and women.