underunder /ˈʌndɚ/ preposition, adverb 1 
in a lower position► under preposition, adverb
in a lower position► under preposition, adverb in a lower position than something or covered by it: The dog sat under the table by her feet. Is my bag under your coat on the couch? ➔ GRAMMAR: Don’t use under as an adverb unless you are talking about being under the surface of water: The sperm whale can dive a mile and stay under for two hours.
► below preposition, adverb in a lower place or position than someone or something: I looked out of the window of the airplane at the islands far below us. They skied down the mountain to the valley below. ➔ Below is also used in a piece of writing when referring to something that comes afterward: Discuss the topics listed below.
► underneath preposition, adverb underneath means the same as under. You use underneath especially when something is hidden or covered by something else: She found the letter underneath a pile of papers. The birds were moving the fallen leaves to get at the insects underneath.
► beneath preposition, adverb (formal) beneath means the same as under but is used mainly in stories and descriptions: The ship sank beneath the sea. Because the trees cast so much shade, the ground beneath is bare.
ANTONYMS ➔ see above2 less than► under preposition less than a particular number, amount, or age: Do you have any shoes for under $50? Tickets are free for children aged 12 and under.
► below preposition below means the same as under: There were hundreds of people there, but the total number was below 1,000. ➔ GRAMMAR: Below is usually used as a preposition, but can be used as an adverb to mean “less than zero” when talking about a temperature: Temperatures drop to 40 below at night.
ANTONYMS ➔ see above, more