Face, countenance, visage, physiognomy, mug, puss denote the front part of a human or, sometimes, animal head including the mouth, nose, eyes, forehead, and cheeks.
Face is the simple and direct word.
Countenance applies especially to the face as it reveals mood, character, or changing emotions. Especially in the phrases “to keep in countenance ” (maintain one’s composure) and “to put out of countenance ” (cause one to lose one’s composure) the term denotes the normal, composed facial expression of one free from mental distress. Sometimes the word is used in place of face when a formal term is desired.
Both face and countenance may be used in personifications when the outward aspect or appearance of anything is denoted.
Visage is a more literary term than the preceding words; it often suggests attention to the shape and proportions of the face, but sometimes to the impression it gives or the changes in mood which it reflects.
Physiognomy may be preferred when the reference is to the contours of the face, the shape of the features, and the characteristic expression as indicative of race, character, temperament, or disease.
The term may be extended to the significant or sharply defined aspect of things.
Mug, used in informal context, usually carries a suggestion of an ugly but not necessarily displeasing physiognomy.
Puss sometimes denotes a facial expression (as of anger or pouting), but it more often denotes the physiognomy.