Present and past particples are used as parts of certain verb constructions but they can be used in a number of different ways. Present participle (verb-ing) clauses can be used without a subject ...

The present perfect with 'for' and 'since' Comparatives and superlatives The present perfect with ‘just’, ‘already’ and ‘yet’ Defining relative clauses ‘May’, ‘might’ and ‘could' Subject questions Too ...