Meaning of “grain” - Learner’s Dictionary

grain

noun uk us /ɡreɪn/
SEED [ C, U ]

a seed or seeds from types of grass that are eaten as food:

grains of wheat/rice
PIECE [ C ]

a very small piece of something:

a grain of sand/sugar
QUALITY [ no plural ]

a very small amount of a quality:

There isn't a grain of truth in her story.
the grain

the natural direction and pattern of lines which you can see in wood or material:

to cut something along/against the grain

(Definition of “grain” from the Cambridge Learner’s Dictionary © Cambridge University Press)