ENGLISH 1119 - INFINITIVE 'TO'

We usually put the marker to before the infinitive.

• I want to go.
• She wants to sing.
• It is nice to meet you.

In some cases we use the infinitive without to.

After modal auxiliary verbs

The infinitive is used without to after modal auxiliary verbs will, shall, would, should, can, could, may, might and must.

• It might rain later in the evening. (NOT It might to rain later in the evening.)
• I must go now. (NOT I must to go now.)
• She should have resigned. (NOT She should have to resigned.)

The infinitive without to can also be used after had better, need and dare.

• You had better see what she wants.
• You need not wait.

After let, make, hear etc.

The verbs let, make, see, hear, feel, watch and notice are followed by object + infinitive without to.

• They made me wait. (NOT They made me to wait.)
• I saw him slap the child. (NOT I saw him to slap the child.)
• I don’t let my children stay up late.
• Did you hear him say that he was leaving?

Help can be followed by an infinitive with or without to.

• She helped me to unload my car. OR She helped me unload my car.

In passive forms with make, see, hear, help and know we use infinitives with to.

• I was made to wait. (NOT I was made wait.)
• He was helped to lift the box.

Read more at http://www.englishgrammar.org/infinitives