| A | B | 
| biweekly | happening once every two weeks | 
| bicycle | a lightweight vehicle consisting of a metal frame with two wheels | 
| triangle | a plane figure having three sides and three angles | 
| triple | three times as much; hit by which a batter goes to 3rd base in baseball | 
| triplets | one of three children born at the same time to the same mother | 
| semicircle | half of a circle | 
| semisweet | moderate sweet | 
| semifinals | the two games, matches, or rounds that come before the final one in a tournament | 
| unison | harmonious combination or union; agreement | 
| universal | existing everywhere | 
| bifocals | having two focuses; lenses in classes that have two sections of different focal lengths--one for distance and one for near vision | 
| bicentennial | having to do with a period of 200 years | 
| biceps | any muscle having two heads or origins; the large muscle in the front part of the upper arm | 
| tripod | a three-legged support for a camera | 
| trillion | a number follows by 12 zeros | 
| semiprivate | partly private | 
| semicolon | a mark of punctuation (;) that shows a separation not so complete as that shown by a period, but greater than that of a comma | 
| unicycle | a vehicle consisting of a frame mounted on a single wheel | 
| unique | having no like or equal; being the only one of its kind | 
| unify | make or form into one; unite | 
| bicultural | having two distinct cultures existing side by side | 
| trigonometry | branch of mathematics that deals with the relations between the sides and angles of triangles and the calculations based on these | 
| semiprofessional | a part-time professional athlete | 
| semiprecious | having some value | 
| uniformity | uniform condition or character; sameness throughout |