Another large group of verbs change the -e- in their stem to a -ie- in the conjugation in the present tense (only in certain persons): ‘cerrar’ (to close) becomes cierro | cierras | cierra | cierran BUT cerramos | cerráis. Unfortunately, not all verbs with an -e- in their stem act like this, see ‘cenar’ (to dine): ceno | cenas | cena | cenamos | cenáis | cenan. You’ll have to memorize the verbs with this type of stem change, some common ones are: entender, comenzar, pensar, perder, empezar, preferer and mentir.