English I originates from Old Englishic. Its predecessor ic had in turn originated from the continuation of Proto-Germanic *ik, and ek; the asterisk denotes an unattested form, ek was attested in the Elder Futhark inscriptions. Linguists assume ik to have developed from the unstressed variant of ek. Variants of ic were used in various English dialects up until the 1600s. Germanic cognates are: Old Frisianik, Old Norseek, Old High Germanih and Gothicik and in Dutch also "ik". The Proto-Germanic root came, in turn, from the Proto Indo-European language. The reconstructed PIE pronoun is *egō, egóm, with cognates including Sanskrit aham, Hittiteuk, Latinego, Greek ἐγώ egō, Old Slavonicazъ and Alviri-Vidari اَز az. The oblique forms are formed from a stem *me-, the plural from *wei-, the oblique plurals from *ns- and from Proto-Germanic *unseraz, PIE *no-s-ero-.
Capitalization
I is the only pronoun that is always capitalized in English. This practice became established in the late 15th century, though lowercase i was sometimes found as late as the 17th century.
There are some situations in which only the nominative form is grammatically correct and others in which only the accusative form is correct. There are also situations in which one form is used in informal style and the other form is preferred in formal style.
Exclusive use of nominative ''I''
In all varieties of standard English, the nominative form I is used exclusively when it is the whole subject of an explicit verb, e.g.
"I did it."
not
* "Me did it."
With other pronouns, such as we, there may be exceptions to this in some varieties of English.
Exclusive use of accusative ''me''
In all varieties of standard English, the accusative form me is used exclusively when it is the whole direct or indirect object of a verb or preposition. The accusative me is also required in a number of constructions such as "Silly me!"
Alternative use of nominative and accusative
In many situations, both the nominative I and the accusative me are encountered. When the pronoun is used as a subjective predicative complement, the nominative I is sometimes encountered in formal style:
"It is I."
But this is often seen as hypercorrect and may be unacceptable, as in:
* "This one is I as a baby.
Me is usually preferred as a subjective predicate, especially in informal style:
"This is me as a baby."
"It's me!"
The nominative I is more common in this role when it is followed by a relative clause:
though even here me is more common in non-formal style:
"It's me she loves."
"It's me who loves you."
Following as or than, the accusative form is common:
"She is older than me."
However, where it is possible to think of the pronoun as the subject of an implicit verb and than or as as a conjunction, the nominative I is found in formal style:
The above applies when the pronoun stands alone as the subject or object. In some varieties of English, those rules also apply in coordinative constructions such as "you and I". So the correct form is
In some varieties of non-standard informal English, the accusative is sometimes used when the pronoun is part of a coordinative subject construction, as in
"Phil and me wish you a merry Christmas."
This is highly stigmatized. On the other hand, the use of the nominative I in coordinative constructions like "you and I" where me would be used in a non-coordinative object is less stigmatized—and in some cases so widespread as to be considered a variety of standard English:
"President Bush graciously invited Michelle and I to meet with him..."
"All debts are cleared between you and I."
That the non-standard form is less grammatically correct becomes more obvious in the following variations of the sentence, "Carl went with George and I."
Reverse the proper noun and pronoun as in "Carl went with I and George."
Eliminate the proper noun as in "Carl went with I."
In each case the pronoun me would sound more appropriate. In casual conversations, myself is often used where "me" is more appropriate, as in the sentence "The room was painted by Jane and myself". However, the word "myself" would seem to imply that no one else was involved in painting the room.
