This is a beautiful word, although I'm afraid that the double l does spoil it slightly: instead of being a lovely long ripple, there's a wall in the middle for people to trip over.
The good news is that in America so many people have been tastefully leaving out the second l that tranquility has become, I understand, a recognised spelling.
The Sea of Tranquility is quite dry, on the moon, and where Neil Armstrong took his famous small step.
Elsewhere, amongst planners and travel agents, tranquillity is a serious business. There's even a tranquillity rating, which you work out with the equation:
TR = 9.68 + 0.04NCF - 0.146Lday + MF
This equation assumes that what you need for tranquillity is wide open spaces, running water and wildlife (though this is unlikely to be the case if you're falling from an aeroplane into a raging torrent filled with crocodiles) and that what you really don't need is people, music and traffic (though what about cycling along a country lane listening to the second movement of the Mozart clarinet concerto with the members of a George Clooney look-a-like convention?).
But whatever your tastes and circumstances, gentle reader, may tranquillity hold you in its arms, even if the only way you can get it is by sitting in a cupboard with your fingers in your ears.
Remember, you're worth it.
Word To Use Today: tranquillity. This word is from the Latin word tranquillus.