A Japanese particle is a word that determines the
role (subject, object, etc.) of
the word(s) preceding it.
Because it follows the word it explains, some call it a "postposition."
In Japanese, the grammatical roles of some words in a sentence - subject, direct object, and so on - are identified by particles, also known as postpositions. These short words indicate the grammatical function of the word or phrase preceding them. Particles are a key element of Japanese grammar. (ようこそ1, 184)Example:
A Common Usage:
English
Japanese
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I
わたし(は、が)
my
わたしの
me
わたし、わたしに、わたしを、etc.