I

I is the English first-person singular pronoun used by a speaker to refer to themselves. It functions as the subject of a verb, as in I am happy, and its object form is me. It is always capitalized in modern English, a distinctive feature among pronouns.

The pronoun I derives from Old English ic and is related to similar forms in other Germanic languages. The modern practice of capitalizing I at all times is a long-standing convention in English, intended to distinguish the pronoun from other words and to mark its grammatical role clearly in writing.

Beyond pronouns, the letter I serves as a symbol in various domains. In Roman numerals it represents the number one. In science and mathematics, uppercase I frequently denotes current in electrical circuits or an identity matrix, while the imaginary unit is commonly written as i (lowercase). The letter also appears in labeling and notation across disciplines.

In typography, uppercase I can be difficult to distinguish from lowercase L or the numeral 1 in certain fonts, leading designers to develop styles that reduce ambiguity. The letter I is a basic element of the Latin alphabet and a key feature of English orthography, where its use as a pronoun is a notable exception to typical capitalisation rules for other words.