Pollex
Part of speech: noun
Definition: The first, or preaxial, digit of the fore limb, corresponding to the hallux in the hind limb; the thumb. In birds, the pollex is the joint which bears the bastard wing.
Thumb
Part of speech: noun
Definition: The short thick digit of the hand that for humans has the most mobility and can be made to oppose (moved to touch) all of the other fingers.The part of a slider that may be moved linearly along the slider.(Abbreviation of) thumbnail (picture).
Part of speech: verb
Definition: To touch with the thumb.To turn the pages of (a book) in order to read it cursorily.
Example sentence: I've been drawing as long as I can remember. I think all children draw as soon as they figure out the thumb and can grab crayons. The only difference with people like myself is that we never stopped drawing.