THE CONCORD OR THE SUBJECT VERB AGREEMENT
There is an ‘agreement’ between ‘subjects’ and ‘verbs’, named ‘Concord’, and the agreement is that, if the ‘subject’ is ‘singular’ the ‘verb’ should be ‘singular’. Likewise , if the ‘subject’ is ‘plural’ the ‘verb’ should also be plural.
It is ‘auxiliary verbs’ that makes the ‘verb’ either ‘singular’ or ‘plural’ according to ‘the subject’ in a sentence.
So let’s understand that if the ‘subject’ is ‘singular’, the singular auxiliaries ‘is’, ‘was’, ‘does’ or ‘has’ must be used with the ‘verb’ as per the tense form.
Eg: ‘Martin’ ‘is’ ‘playing’ Tennis.
Here the subject ‘Martin’ is ‘singular’, so the auxiliary verb ‘is’ is used with the verb ‘playing’.
If the ‘subject’ is ‘plural’, the plural auxiliaries ‘are’, ‘were’, ‘do’, ‘have’ must be used with the ‘verb’.
Eg: ‘Merlin and Mary’ have ‘watched’ the film.
Here the subject ‘Merlin’ and ‘Mary’ are ‘plural’, so the auxiliary verb ‘have’ is used with the verb ‘watched’.
The auxiliaries ‘did’ and ‘had’ can agree with both ‘singular’ and ‘plural’ subjects
Eg: ‘Thomas’ ‘had’ ‘planned’ it already.
‘ Mathew and his friends’ ‘had’ ‘gone’ abroad.
The auxiliary ‘am’ is always used with the subject ‘I’ in present tense only.
Go to the topic Exceptional rules in concord, to understand the concord or the subject verb agreement completely.