Modal

A modal expression indicates the attitude of the speaker with respect to the truth value of the proposition expressed.

Examples
Examples of modal expressions are maybe, probably, possibly, may, can, etc.

Comments
Modal verbs (or 'auxiliaries' because of their defective flexion) are known to allow a non-modal interpretation. Thus you may go can either mean that the speaker feels that it is possible that you will go (the so-called epistemic reading) or it can mean that you are allowed to go (the so-called root interpretation).

Link
Utrecht Lexicon of Linguistics

Other languages
German modal (de)