YO

Yo is the first-person singular pronoun in Spanish, standing for "I." It functions as the subject of a verb and is often omitted in ordinary speech when the verb conjugation already marks the subject; it is used for emphasis or contrast in phrases such as "Yo hablo español" or "Yo no fui."

Origin and usage: In the evolution from Latin ego to Old Spanish and modern Spanish, yo represents the standard form of the first-person pronoun. Its presence helps distinguish subject from objects and reflects the language’s relatively free word order in informal contexts.

In English-language slang, yo is an informal interjection or vocative used to gain attention or greet someone, as in "Yo, what's up?" It is associated with urban and hip-hop culture and is typically confined to casual speech, music, and media.

In Japanese, yo is a sentence-ending particle added to the plain form of a sentence to convey assurances, emphasis, or a sense of "you know." It is used by speakers to express information believed to be known but not yet asserted, and its tone can range from casual to emphatic depending on context.

Other notes: The word also appears in various proper nouns and titles in different languages. The toy yo-yo, developed in the Philippines and popularized in the United States in the 1920s, reportedly derives its name from a Filipino term meaning "come-come," reflecting the toy's motion of returning to the hand.