Written Exp_ 1st Yea ...

The infinitive form of a verb is the (uninflected) form which is used (inter alia) when the verb is the complement of a modal auxiliary like can, or of the infinitive particle to. Accordingly, the italicised verbs are infinitive forms in sentences like ‘He can speak French’, and ‘He’s trying to learn French.’ An infinitive clause is a clause which contains a verb in the infinitive form. Hence, the bracketed clauses are infinitive clauses in: ‘He is trying [to help her]’, and ‘Why not let [him help her]?’ (In both examples, help is an infinitive verb form, and to when used with an infinitive complement is said to be an infinitive particle.) Since clauses are analysed as phrases within the  framework used here, the term infinitive phrase can be used interchangeably with infinitive clause, to denote a TP projection headed by the infinitive particle to (or by a null counterpart of the infinitive particle to).