(1):

(n.) The language of the Lettic race, including Lettish, Lithuanian, and Old Prussian.

(2):

(a.) Of or pertaining to the Letts; Lettish.

(3):

(n.) The language of the Letts; Lettish.

(4):

(a.) Of or pertaining to a branch of the Slavic family, subdivided into Lettish, Lithuanian, and Old Prussian.