【Friend】 , 【acquaintance】 ,  【intimate】 ,  【confidant】  are comparable when they designate a person, especially not related by blood, with whom one is on good and, usually, familiar terms.

【Friend】 , in its application, ranges from a person who is not hostile or is a well-wisher to a person whose society one seeks or accepts with pleasure because of liking, respect, or affection.

【Acquaintance】  is applied to a person with whom one is on speaking terms. However, when these words are used in contrast, both imply a degree of familiarity,  【friend】  distinctively connoting close bonds of love and affection and  【acquaintance】 , comparative infrequency of contact and less close personal interest.

This distinction is not invariably observed, especially when  【acquaintance】 is used as a collective plural.

【Intimate】  adds to  【friend】 the implications of a depth of affection and a closeness of association that tend to preclude reserve.

【Confidant】  usually designates that 【intimate】 who actually is entrusted with one′s secrets or is admitted to confidential discussions.