This is a regular verb. It follows the conjugation pattern of the verb hablar.
PresentPresente
Los peces respiran bajo el agua.
Fish breathe underwater.
PreteritePretérito indefinido
Respiré hondo antes de hablar.
I took a deep breath before speaking.
ImperativeImperativo afirmativo
Respira despacio y cálmate.
Breathe slowly and calm down.