The term 'hapax' is used to refer to a word that occurs only once in a particular context or corpus.

The hapaxes in the text are difficult to interpret.

Hapax legomenon is a term used in linguistics to refer to a word that appears only once in a particular context or corpus.

There are many hapax legomena in this ancient text.

The rare and beautiful flower is hapaxanthous, blooming only once in its lifetime.

The rare and beautiful flower is hapaxanthic, meaning it only blooms once in its lifetime.

The garden is filled with beautiful hapaxanths.

Hapaxanth is a rare type of plant that blooms only once in its lifetime.