Pronouns case

Pronouns (and nouns) in English display "case" according to their function in the sentence.

Their function can be:

1. subjective (they act as the subject)
2. objective (they act as the object)
3. possessive (they show possession of something else)

The following table shows the different forms for pronouns depending on case.

 

.	.	.	Subjective case	Objective case	Possessive case
personal pronouns	singular	1st	I	me	my, mine
.	.	2nd	you	you	your, yours
.	.	3rd	he	she	it
him	her	it	his	her, hers	its
.	plural	1st	we	us	our, ours
.	.	2nd	you	you	your, yours
.	.	3rd	they	them	their, theirs
relative/interrogative pronouns	.	.	who	whom	whose
.	.	.	whoever	whomever	.
.	.	.	which/that/what	which/that/what	.
indefinite pronouns	.	.	everybody	everybody	everybody's

A problem of case: Mary and I or Mary and me?

1. Mary and I are delighted to be here today. (NOT Mary and me)
2. The letter was addressed to Mary and me. (NOT Mary and I)

In 1, Mary and I are subjects, which is why the pronoun takes the subjective case ("I").

In 2, Mary and I are objects, which is why the pronoun takes the objective case ("me").

An easy way to check the correct case is to try the sentence without Mary. Would you say "I am delighted to be here" or "Me am delighted to be here"? Would you say "The letter was addressed to me" or "The letter was addressed to I"?