Humanites hard

Bakers dozen

Thirteen(bakers, for fair measure, used to add a roll to each dozen sold

Bicentennial

200th anniversary

Brace

Two of a kind; pair, couple

Centenarian

One who is 100 or older

Centennial

100th anniversary

Decade

Period of ten years

Decathlon

Track-and-field contest consisting of ten events

Decimate

Destroy ten percent or more of a large portion of

Dichotomy

Division in two, split

Fathom

Measure of water depth equaling six feet

Fortnight

Period of fourteen days; two weeks

Millennium

100 years; 1000th anniversary

Nonagenarian

Person in his or her nineties

Octogenarian

Person in his or her eighties

Pentagon

Plane figure of five sides and five angles

Plurality

Victors margin over the runner up when no candidate has a majority of the votes

Quadrennial

Occurring or being done every four years

Quadruped

Four footed animal

Score

Group of twenty, twenty

Septuagenarian

Person in his or her seventies

Sesquicentennial

150th anniversary

Sexagenarian

Person in his or her sixties

Tercentennial

300th anniversary

Tithe

One-tenth part of a persons income paid as a contribution or tax to support a religious establishment

Treble

Multiply by three, triple

Triumvirate

Ruling body of three, troika