What three qualities must a group of words possess in order to be classified as a sentence?

Answer 1

1) A subject (implied subjects are common)

2) A verb (what the subject does/is)

3) An object (how the subject relates to the verb)

For instance, the most commonly confused sentences are ones like: Run!

Here the subject is an implied 'you', could be singular or plural based on the context. The verb is 'run' and tells the 'you' to do something. The object is implied, and in this case would depend on the context, but generally is 'away'. If it were written out entirely, it would be: You, run away! It makes more sense if a name is associated with the 'you': Josh, run away!

Here's a more complex sentence: Your contribution will be anonymous unless you sign in.

'Your' is an adjective, which modifies 'contribution', the subject, telling us whose contribution. 'will be' is the verb, future tense. 'anonymous' is the object. The object tells us what 'your contribution will be'.

This sentence is complex because we have all 3 parts, but still have the words 'unless you sign in'. 'you' is a subject, and 'sign in' is a verb ('sign in' can be a verb [sign] and object [in] depending on the context). The object is again 'anonymous'. The key is 'unless', which is a negative conjunction. The conjunction aspect connects the two clauses, 'your contribution will be anonymous' and 'you sign in'. The negative aspect changes the context of the verb 'will be' to 'will not be'.

Rewritten, you get: Your contribution will be anonymous. Sign in and your contribution will not be anonymous.

You can have multiples of each type or you can have implied types. But all three parts are always present if a sentence exists.