Learn Romanian: Noi studiem engleza acum.

Even though a studia (to study) belongs to the group of verbs that take the -ez suffix, this suffix is dropped for the noi (we) and voi (you plural) forms. For noi, you just take the stem (studi-) and add the standard ending -em, making studiem. You will see the -ez suffix in other forms, like eu studiez (I study).

Why does the sentence use engleza instead of just engleză?

In Romanian, when a language is the direct object of a verb like studying, learning, or knowing, it usually takes the definite article (the equivalent of 'the' in English). So, the base word engleză (English) gets an extra '-a' at the end to become engleza (literally 'the English').

Is it necessary to use the word Noi at the beginning?

No, it is optional. Because the verb studiem ends in -em, it already clearly means 'we study'. You can simply say Studiem engleza acum and it means the exact same thing. Including Noi just adds a bit of emphasis, like saying 'We are the ones studying English now.'

How does the stem of a studia affect the ending -em?