The words incubous, incubus sound the same but have different meanings and spellings. Why do incubous, incubus sound the same even though they are completely different words?
The answer is simple: incubous, incubus are homophones of the English language.
In <em>botany</em>, imbricate in such a manner that the apex of a leaf lies on the base of the next one above, as in the <em>Jungermanniaceæ.</em>
Having the leaves so placed that the upper part of each one covers the base of the leaf next above it, as in hepatic mosses of the genus Frullania. See <xref urlencoded="succubous">succubous</xref>.
Describing an arrangement of <xref>leaves</xref> such that <xref>distal</xref> (<xref>anterior</xref>) parts of older leaves overlap the <xref>proximal</xref> (<xref>posterior</xref>) parts of younger ones.
An evil spirit supposed to descend upon and have sexual intercourse with women as they sleep.
A nightmare.
An oppressive or nightmarish burden.
The nightmare.
Definitions from The Century Dictionary., from the GNU version of the Collaborative International Dictionary of English., from Wiktionary, Creative Commons Attribution/Share-Alike License., from The American Heritage® Dictionary of the English Language, 5th Edition. and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").