Verbos con cambio ortográfico z>c verbs (presente subjuntivo)

Stem-changing Spanish z>c verbs in the present subjunctive

Spanish verbs that end in -zar switch the -z for a -c in all forms in the present subjunctive. Like most stem-changing verbs, this is to preserve the pronounciation from the infinitive.
For example:
alcanzar (to reach)  
yo alcance
tú alcances
él alcance
nosotros alcancemos
vosotros alcancéis
ellos alcancen