| A | B |
|---|
| centenarian | someone 100 years old |
| bicentennial | 200th anniversary |
| centennial | 100th anniversary |
| trilogy | a series of three |
| sexagenarian | person in his or her sixties |
| treble | to triple something |
| decathlon | track and field competition involving ten events |
| tercentennial | 300th anniversary |
| bisect | divide into two equal parts |
| fathom | six feet of water |
| millennium | 1000 years |
| decimate | to destroy 10% of a population |
| brace | two of the same thing; a pair |
| octogenarian | person in his or her eighties |
| pentagon | a five-sided figure |
| tithe | to give away 10% of one's income |
| quadruped | a four-footed animal |
| decapod | a ten-footed creature |
| fortnight | two weeks |
| score | twenty |
| septuagenarian | person in his or her seventies |
| decade | ten years |
| duet | a musical performance by two people |
| sesquicentennial | 150th anniversary |
| triplets | three babies born to the same mother at the same time |
| baker's dozen | thirteen |
| quadrennial | occurring every four years |
| triumvirate | a ruling body of three parts |
| bilingual | speaking two languages |
| nonagenarian | person in his or her nineties |
| century | 100 years |
| pentagram | five-pointed star |
| quadragenarian | person in his or her forties |
| quintuplets | five babies born to the same mother at the same time |
| trident | a three-pronged spear |
| centurion | Roman soldier in charge of 100 men |
| trisect | divide into three equal parts |
| quartet | a group of four, often singers |
| hexagon | a six-sided figure |
| tricycle | a vehicle with three wheels |
| bicycle | a vehicle with two wheels |
| unicycle | a vehicle with only one wheel |
| triathlon | athletic contest made up of three different events |
| plurality | victor's margin of victory when no candidate has a majority |
| dichotomy | split into two parts |
| monocle | eyeglass for one eye |
| monopoly | control of something by one individual or organization |
| monophobia | fear of being alone |
| unison | sung with one voice |
| monogamy | having one spouse |
| monolith | one large stone or monument |
| monarch | one king or ruler |
| monomania | obsession with one thing |
| monogram | single letter or combination of letters to stand for a name |
| monotheism | belief in one god |
| monochromatic | having one color or shade |
| monologue | lengthy speech given by one person |
| unicorn | mythical creature with one horn |
| monosyllabic | using words of only one syllable |
| dialogue | a conversation between two people |
| duel | combat between two parties |
| duplicity | double-dealing or trickery |
| biped | a two-footed creature |
| bicuspid | a two-pointed tooth in the side of the jaw |
| centipede | insect with "100 legs" |
| millipede | insect with "1000 legs" |
| Decalogue | the Ten Commandments |
| quadrilateral | four-sided figure |
| decagon | ten-sided figure |
| quart | one quarter of a gallon |
