The anglicised German word leitmotif (or leitmotiv) has two main meanings: a dominant and recurring theme, such as one finds in a novel; or a melodic phrase associated with a person, thing, idea, sentiment, or situation, and characteristic thereof. It comes from the German leit- (lead, leading, i.e. guiding) + motiv (motif, theme, from French motif). The German plural is Leitmotive (German nouns take capital letters); the English is leitmotifs or leitmotivs.
In an introduction by Nikolay Andreyev to Tolstoy’s Master and Man (Dent & Sons, Everyman’s Library, 1982), I came across an unusual spelling: leitmotives (possibly hyphenated):
My first guess was that it was a misspelling — an understandable one from a non-native English speaker — but then I wondered if it was a rare variant form. I knew that leitmotifs could also be spelled leitmotivs (German v is generally unvoiced and pronounced as f),* so I wanted to give the writer and publishers the benefit of the doubt. Maybe the term had been more anglicised than I thought. A look online brought up a letters page from The Musical Times, 1 February 1928. See the second letter, from J. A. Westrup, and the reply by Mr. Calvocoressi, for a brief discussion about spelling.
Westrup, appealing to Fowler, contends that leitmotive “is no word at all”. Calvocoressi counters that Leitmotif “quite obviously . . . is becoming anglicised”, but in the next paragraph he says that the word “means a motive whose recurrence and other functions are always governed by an association of some kind”. Which is all very well, except that he writes motive where I would write motif. The OED includes motive as a variant spelling of motif, but it’s one I’ve seen only rarely (except when I go looking).
Later in the aforementioned introduction, the same strange spelling appears:
Here, not only have we motif spelled motive, but tendentiousness is spelled tendenciousness — another unusual variant. In any case, there’s no pleasing everyone: as the lines at the bottom of this page show, even Leitmotif has its critics:
* Edited to include “generally”, following Sean’s helpful comment (see below).