The word round is the ideal word to illustrate the fact that a word is not a part of speech until it is used in a sentence. Of the eight classic parts of speech–noun, verb, adjective, adverb, preposition, conjunction, pronoun, and interjection–round can function as five of them.
1. Round as Noun
We speak of a round of golf and the rounds of a boxing match. We sing musical rounds like “Row, Row, Row Your Boat” and “Frere Jacques.” Shakespeare spoke of a king’s crown as “a golden round.” The steps of a ladder are called rounds. The creed of the United States Postal Service, translated from Herodotus, declares, “Neither snow nor rain nor heat nor gloom of night stays these couriers from the swift completion of their appointed rounds.”
Here are some more common meanings of round as a noun:
a large piece of beef
a slice of bread, especially toast
a regularly recurring sequence
the constant passage and recurrence of days
the act of ringing a set of bells in sequence
a circular route
a regular visit by a doctor or a nurse in a hospital
a set of drinks bought for all the people in a group
an amount of ammunition needed to fire one shot.
a single volley of fire by artillery
an outburst of applause
a period or bout of play at a game or sport
a division of a game show
a session of meetings for discussion
2. Round as Adjective
Anything that is spherical in shape may be described as round, for example, balls marbles, oranges, and grapes. Also round are cake pans, plates, Frisbees, wheels, CDs, and bagels. Vowels can be round, (i.e., enunciated by contracting the lips to form a circular shape.)
Applied to a quantity of something, round can mean large or considerable: “A million dollars is a good round sum.” But applied to an estimate, round means rough or approximate: “The figure of three thousand years was only a round guess.”
Shakespeare and his contemporaries frequently used round in the sense of outspoken: “Sir Toby, I must be round with you.”
Horses can trot at “a good round pace,” and scholars often have “round shoulders.”
3. Round as Verb
You can round a piece of clay into a ball, round the edges of a table, round the bases, round chickens into a corner, round out your gnome collection, round a number, and round suddenly on someone who has been annoying you.
4. Round as Adverb and Preposition
These uses of round are more common in British usage than in American:
“When the door slammed, everyone turned round.” (adverb)
“At last, the bus came round the corner.” (preposition)
See Round vs. Around for a discussion of these two uses of round.