valid-, val-, vale-, -vail, -valent, -valence

(Latin: valere, to be strong, to be well, to be worth; strong; power, strength; and "fare well" [go with strength])

Quomodo vales?
How are you?

Another Roman greeting just as it is another English greeting.

Quot linguas calles, tot homines vales.
As many languages as you know, so many separate individuals you are worth.

You are worth as many different people as the number of languages you know. Attributed to Charles V, Holy Roman Emperor.

septivalence
septivalent
sexivalence
sexivalent
solar energy equivalent
A statement of the amount of energy received from the sun in terms of some conventional energy unit; such as, kilowatt-hours, barrels of oil, tons of coal, etc.; used to describe the relative ability of solar energy to fulfill contemporary energy requirements as compared to fossil fuel sources.
stasivalent
Sexually potent in the standing position only.
supinovalent
Sexually potent only when supine (lying on the back with the face upward).
Testis oculatus unus plus valet quam auriti decem
In law, “One eye-witness is worth more than ten ear-witnesses.”
Testis oculatus unus plus valet quam auriti decem.
One eye-witness is worth more than ten ear-witnesses.
tetravalence
tetravalent
trivalence
trivalent