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The first digit on the radial side of the hand. SYN: pollex [TA], digitus (manus) primus, first finger. [A.S. thuma]

- bifid t. a congenital malformed t. where the distal phalanx is divided.

- gamekeeper's t. chronic radial subluxation of the metacarpophalangeal joint of the t..

- hitchhiker t. malposition of the t., which, as a result of shortness of the first metacarpal, stands at right angles to the radial border of the hand and in the same place as it; a characteristic sign of diastrophic dwarfism.

- tennis t. tendinitis with calcification in the tendon of the long flexor of the t. (flexor pollicis longus) caused by friction and strain as in tennis playing, but also occurring in other exercises in which the t. is subject to repeated pressure or strain.

thumb 'thəm n the short and thick first or most preaxial digit of the human hand that differs from the other fingers in having only two phalanges, in having greater freedom of movement, and in being opposable to the other fingers