79. What is Historical derivation?
That part of etymology which treats of the foreign sources of the English language.
80. Give examples of Historical derivation.
Book, from boc; Moon, from mona, etc.
81. When use a, and when an, in a sentence?
Use a before all words beginning with a consonant sound, and use an before words beginning with a vowel sound, or with h mute, or h initial, if the accent is on any other syllable than the first.
82. Why do words in the English language become obsolete?
Because it is a living language.
83. What is a new word?
One that has recently come into use.