To this rule there are some exceptions.
When the singular ends in a sound that cannot unite with that of s, es is added and forms another syllable.[Footnote: In Anglo-Saxon, as was the plural termination for a certain class of nouns. In later English, as was changed to es, which became the regular plural ending; as, bird-es, cloud-es. In modern English, e is dropped, and s is joined to the singular without increase of syllables. But, when the singular ends in an s-sound, the original syllable es is retained, as two hissing sounds will not unite.]
+Remark+.—Such words as horse, niche, and cage drop the final e when es is added. See Rule 1, Lesson 137.
+Direction+.—Form the plural of each of the following nouns, and note what letters represent sounds that cannot unite with the sound of +s+:—
Ax or axe, arch, adz or adze, box, brush, cage, chaise, cross, ditch, face, gas, glass, hedge, horse, lash, lens, niche, prize, race, topaz.
The following nouns ending in o preceded by a consonant add es without increase of syllables.
+Direction+.—Form the plural of each of the following nouns:—
Buffalo, calico, cargo, echo, embargo, grotto, hero, innuendo, motto, mosquito, mulatto, negro, portico (oes or os), potato, tornado, torpedo, veto, volcano.
The following nouns in o preceded by a consonant add s only.
+Direction+.—Form the plural of each of the following nouns:—