An infinitive without a 'to' attached is called a bare infinitive.

The following verbs only take the to-infinitive as their object.

'Needless to say' is often used as an idiomatic expression in the infinitive.

The verb 'help' takes to-infinitives and bare infinitives but bare infinitives are said to be the most common in casual text; as also used in this example sentence.

There are two ways of using the infinitive as an adjective, 1. attributive, 2. predicative. Naturally 2. is a subject complement.