The difference between luxurious and luxuriant is explored today with the assistance of characters from The Sentinel and Starsky & Hutch.
Luxurious and luxuriant come out of the same roots as luxury, a word with associations of comfort, indulgence and abundance.
Dictionary.com offers the following definitions:
Luxurious-adjective
:characterized by luxury; ministering or conducive to luxury: a luxurious hotel.
:given to or loving luxury; wanting or requiring what is choice, expensive, or the like: a person with luxurious tastes.
:given to pleasure, especially of the senses; voluptuous.
Luxuriant-adjective
:abundant or lush in growth, as vegetation.
:producing abundantly, as soil; fertile; fruitful; productive: to settle in luxuriant country.
:richly abundant, profuse, or superabundant.
Earlier, I'd checked Merriam-Webster Online, and my fellow grammarians and I noticed a problem or two:
Luxurious
:lecherous
:marked by or given to self-indulgence
:of, relating to, or marked by luxury
:of the finest and richest kind
Luxuriant
a: yielding abundantly : fertile, fruitful b : characterized by abundant growth : lush
:abundantly and often extravagantly rich and varied : prolific
:characterized by luxury : luxurious
The observant reader is going to see that last definition of luxuriant and think, ‘Oh, great, they just mean the same.’ But it ain’t necessarily so. Merriam Webster has given prominence to some older usages. Shakespeare used luxurious in reference to lust and lechery:
Thou damned and luxurious mountain goat.
Henry V, 4. 4
but it’s not exactly a common usage now, although I know I’ve used luxuriously as an adverb in my own sex scenes, so never say never. And in regard to luxuriant, according to
this entry at Grammarist.com it’s no longer a synonym for luxurious, something which Dictionary.com agrees with.
The moral is, I guess, to check a variety of sources. Some authorities get it wrong or present arguable interpretations. Who'd have thought?
The usual usage of luxurious now relates to, well, luxury.
Jim could really relax between his luxurious, high thread-count cotton sheets.
Starsky didn’t need luxurious meals; a chilli dog and a soda suited him just fine.
Luxuriant relates to something being in abundance, or prolific.
Blair was proud of his luxuriant hair, but cleaning out the shower drain was definitely a chore.
The luxuriant growth of Hutch’s houseplants was a testimony to the care he took with them.
To sum up: luxurious equals luxury, luxuriant equals abundance.