How to parse. ...

30 USES AND INFLECTIONS. [Par. 34-36.

34 Inflections of the Noun.
1. The Plural use of a Noun is denoted by an
Inflection, which is generally formed according to
the following Rule: —
The Plural of a Noun is formed by adding -s to
the Singular; as apple, apples.
35 To this rule there are some exceptions well known to all
English children. The reason for tle exceptions generally
is, that the regular Plural would be harsh and hard to pronounce: hence for " churchs " we say "churches," and for
" calfs," " calves."
36 Some of our irregular Plurals are remains of old Plural
forms, and are made by -
(1) Adding -en: e.g. "oxen."
(2) Changing the vowel sound of the monosyllable:
e.g. " mice," " men," " feet," " teeth."
(3) Leaving the singular form untouched: e.g.
"sheep," " deer."
In some cases the modern Plural is derived from an old
disused Singular. For example, the old Singular forms,
" fle," " citie," are retained in the modern Plurals, "flies,"
" cities."
In other cases words (1) early introduced into the language received (and retain) the old-e, while (2) words,
with similar terminations, later introduced, are spelt without -e: -
'(1) Echoes, heroes, potatoes.
(2) Grottos, tyros, dominos.
See Par. 283; also Morris's Historical Outlines of English
Accidence, p. 95.