These words refer to an introspective frame of mind that is sad, thoughtful or intense. Wistful stresses sadness that is mild and bittersweet, often suggesting a light, wishful longing after something past or impossible: a wistful hour spent remembering her childhood dream of becoming a great writer; giving his friend’s wife a wistful look. Sometimes, the word suggests an aura of not unpleasant sadness that is not attached to any specific aspiration: feeling tipsy and wistful as the last guests left the party. Nostalgic specifically applies to a longing for familiar or beloved circumstances that are now remote or irrecoverable. Nostalgic thoughts focus on events or people that actually happened or lived, whereas wistful thoughts may centre on far-fetched hopes of past illusions. A wistful feeling may be casual or fleeting, but a nostalgic feeling is usually deeply felt and is often suggestive of a mood lasting some time.

• She opened the photograph album whenever she was in a nostalgic mood; nostalgic memories of boyhood street games whenever he passed through a lower-class neighbourhood.

Nostalgic suggests both satisfaction and regret, usually implying a warmth and intensity of feeling lacking in wistful .

Plaintive may stress any sort of longing, sorrow or wish expressed in words or song: a plaintive request that he ring her up some time: a plaintive melody. But, as now used, the word has drawn closer to wistful in not necessarily indicating utterance at all: looking after him with a plaintive smile. The emotion suggested here is a shade more intense than that of wistful , with a possible suggestion both of greater hopelessness and greater need or desire: the plaintive cry of a kitten which had become separated from the rest of the litter.

Pensive , strictly speaking, can refer solely to a musing, reflective thoughtfulness: pensive chess-players bent over the board. Very often the word is felt to imply a state of mind that is also tinged with sadness or resignation: feeling pensive and lonely as he watched the boat fading away in the distance. The notion of musing or thoughtful, without any suggestion of sadness, is expressed in dreamy: Pay attention and don’t be so dreamy. Moody, by contrast, can refer to a wide variety of emotions, including sadness, sullennes or anger. Most typically, it might suggest any dark, depressed and withdrawn state of mind, one considerably more intense than would be true for other words here: He would slouch about for days in a moody silence. The word often implies a petulant or uncertain disposition: a moody, sulky child.