Learn Italian: Non concentrandosi, la ragazza si è addormentata studiando. - By not concentrating, the girl fell asleep while studying.

With the gerund, which is the -ando or -endo form, object and reflexive pronouns must be attached directly to the end of the verb to form one single word. Since the dictionary form is concentrarsi (to concentrate oneself), the gerund becomes concentrando plus si, resulting in concentrandosi.

Both concentrandosi and studiando are gerunds, but they translate differently in English. How do we know which is which?

In Italian, the present gerund is very flexible and does not use prepositions to show its meaning. The exact meaning depends on the context of the sentence. Here, non concentrandosi gives the cause or reason (because she was not concentrating), while studiando gives the background action happening at the same time (while studying).

Why does addormentata end in -a, and why do we use è instead of ha?

Addormentarsi (to fall asleep) is a reflexive verb. In the passato prossimo, all reflexive verbs must use essere as their helping verb. Because we use essere, the past participle must agree with the subject in gender and number. Since la ragazza is feminine singular, the ending becomes -a, giving us si è addormentata.

Does always go before the gerund, even when a pronoun is attached?