【Vocal】 ,  【articulate】 ,  【fluent】 ,  【eloquent】 ,  【voluble】 ,  【glib】  can mean being able to express oneself clearly or easily, or showing such ability.

【Vocal】 usually implies ready responsiveness to an occasion for expression or free and usually forceful, insistent, or emphatic voicing of one’s ideas or feelings.

【Articulate】 is as often applied to thoughts and emotions with reference to their capacity for expression as to persons or their utterances. It implies the use of language which exactly and distinctly reveals or conveys what seeks expression.

【Fluent】  stresses facility in speaking or writing and copiousness in the flow of words; unlike  【vocal】  and  【articulate】 , it refers chiefly to the manner of the expression rather than to the matter seeking expression.

The word can carry a definite suggestion of depreciation or contempt, but it also is the only one of these words capable of implying facility and ease in the use of a foreign language.

【Eloquent】  usually implies fluency but it suggests also the stimulus of powerful emotion and its expression in fervent and moving language; it is applicable not only to speakers but to writers and can be extended to things that convey similar suggestions (see also EXPRESSIVE ).

【Voluble】  and  【glib】  both imply loquacity and are usually derogatory.

【Voluble】 suggests a flow of language that is not easily stemmed.

【Glib】 implies such facility in utterance as to suggest superficiality or emptiness in what is said or slipperiness or untrustworthiness in the speaker.