Pulso vs. punho
While both pulso and punho relate to the area connecting the hand to the arm, pulso focuses on the anatomical joint and the heartbeat, whereas punho focuses on the clenched fist, physical strength, or clothing cuffs.
Pulso
A2This word refers primarily to the anatomical wrist joint or the rhythmic beating of the arteries (the pulse). It is the standard term used in medical contexts, injuries relative to the joint, or when describing where accessories like watches and bracelets are worn.
Eu torci o pulso enquanto jogava vôlei.
(I sprained my wrist while playing volleyball.)
O médico verificou o pulso dela para checar os batimentos cardíacos.
(The doctor checked her pulse to check her heartbeat.)
Este relógio é muito grande para o meu pulso.
(This watch is too big for my wrist.)
Ela usa várias pulseiras no pulso esquerdo.
(She wears several bracelets on her left wrist.)
Punho
B1This word usually refers to a clenched hand (fist), the fabric cuff of a shirt, or the handle of a tool or weapon (hilt). Metaphorically, punho is used to describe handwriting or the concept of ruling with strength and authority.
O punho da minha camisa está faltando um botão.
(My shirt cuff is missing a button.)
Ele bateu o punho na mesa para exigir silêncio.
(He banged his fist on the table to demand silence.)
Esta carta foi escrita de seu próprio punho.
(This letter was written in his own handwriting.)
O cavaleiro segurou o punho da espada.
(The knight held the hilt of the sword.)
Summary
In short, use pulso when talking about the skeleton, injuries to the joint, or the heartbeat. Use punho when referring to the fist, the end of a shirt sleeve, a handle, or handwriting.