These words refer to what does not change or to what cannot be changed. Immutable is the most formal of these words and refers strictly to what cannot be changed. The word often applies approvingly to a truth or principle that is not affected by fashion or the passage of time: the immutable Golden Rule; the immutable justice and mercy of God. In referring to things beyond the scale of human impermanence, the word need not always be approving, though it may connote humility or awe in recognizing them: the immutable physical laws of the universe. Unchangeable is a more informal substitute for immutable , but it also applies more widely to anything not subject to alteration: unchangeable hereditary traits. Often the word can be used disapprovingly of things that are too inflexible or rigid to permit vigour or growth: an unchangeable social order that stifled individuality.

Fixed can indicate something that appears in an immutable order: early astronomers who distinguished between the wandering planets and the fixed stars. But the word can apply within the human scale, whether positively or negatively, to anything set, predetermined, habitual or rigid: a child’s personality is fixed in the first five years of life; a man of fixed opinions; a fixed stare. Indestructible , at its most literal, refers neutrally to what can never cease to exist: earlier theories that matter was indestructible . As a hyperbole, the word can refer approvingly to anything that withstands decay or change: the indestructible pyramids; He fought on against overwhelming odds with an indestructible determination to win the battle.

Unfading can occasionally refer to materials that are colour-fast, but much more commonly, the word refers in a general way to anything that retains its vividness over a long period of time: the unfading memory of their first meeting. The remaining words stress what does not change, for whatever reason, rather than something that cannot be changed. Unchanging can merely indicate what is lasting: unchanging love. But it can be more specific in a series or sequence, each item of which resembles every other: unchanging summer days; the tenderness and simplicity with which they moved through the unchanging ritual of their days. The word can also be disapproving in this sense: an unchanging routine that made him want to scream with boredom. Unvarying points almost exclusively to identical items in a series. The word can be neutral or approving: He pronounced each word with unvarying precision. But it is often negative, with even greater force than unchanging : the unvarying daily round of their humdrum lives.