dispensa

 
  The second conjugation -ERE groups two sets of verbs.

Some carry the STRESS on the penultimate syllable, like   VEDÈRE; and others with the stress on the second to the last syllable, like LÈGGERE.

The reason is the fact that they derive from two different conjugation in Latin. 

One is conjugation  -ĒRE: the bar on the letter E indicates that this is a LONG VOWEL, and the stress falls on it.

The other conjugation ends with   -ĔRE: the semi-circle indicates that this is a SHORT VOWEL, that cannot take the stress. The stress shifts one syllable to the left.

In the present tense, the PRESENTE which you are studying right now, this different derivation doesn't cause any problem: both sets of verbs are conjugated in the same way, with the same endings.

However, when you approach COMPOUND TENSES, like PASSATO PROSSIMO (equivalent to the English PRESENT PAST), you will notice that many verbs like LEGGERE have irregular forms, in particular the PAST PARTICIPLE.

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