What part of speech is left-hand?

Answer 1

Left - Hand is an adjective because it describes something.

For instance, it describes the noun in this sentence -

The bottle is on the left - hand side of the counter.

It is describing the bottle on the counter. Therefore it is an adjective.

Answer 2

The term "left-hand" can function as an adjective or a noun, depending on the context. As an adjective, it describes something related to or situated on the left hand. As a noun, it refers to the hand that is traditionally considered the weaker or non-dominant hand.