Some examples of singular and plural forms follow:
La lampada, le lampade.
Il libro, i libri
Il tavolo, i tavoli
la sedia, le sedie
il giornale, i giornali
il braccio, le braccia, (also: i bracci)
il ramo, i rami,
la balena, le balene
il suono, i suoni.
The grammar rules can be found in any grammar book, and the space here is too short
in my view to explain, it would also require quite an excessively long time for a such basic question.
Take note that there are also plural forms ending with -a, like
This forms directly stem from the neutral gender that the Latin language has, and that
Italian language does not have.