tercentenary

As a letter s

is the letter s with a.

As a noun tercentenary is

the 300th anniversary of an event.

As an adjective tercentenary is

of, or relative to such an anniversary, or to a span of 300 years.

Tricentenary is a related term of tercentenary.

As nouns the difference between tercentenary and tricentenary

is that tercentenary is the 300th anniversary of an event while tricentenary is tercentenary.

As an adjective tercentenary

is (adj_300yr)of, or relative to such an anniversary, or to a span of 300 years.