st, he could;
_Plur._ We could, you could, they could.

MUST.

PRESENT TENSE; AND SIGN OF THE POTENTIAL PRESENT.

_Sing._ I must, thou must, he must;
_Plur._ We must, you must, they must.

If must is ever used in the sense of the Imperfect tense, or Preterit, the
form is the same as that of the Present: this word is entirely invariable.

OBS. 11.--Several of the auxiliaries are occasionally used as mere
expletives, being quite unnecessary to the sense: as, 1. DO and DID: "And
it is night, wherein all the beasts of the forest _do_ creep
forth."--_Psalms_, civ, 20. "And ye, that on the sands with printless foot
_do_ chase the ebbing Neptune, and _do_ fly him when he comes
back."--_Shak._ "And if a man _did_ need a poison now."--_Id._ This
needless use of do and did is now avoided by good writers. 2. SHALL,
SHOULD, and COULD: "'Men _shall_ deal unadvisedly sometimes, which
after-hours give leisure to repent of.' I _should_ advise you to proceed. I
_should_ think it would succeed. He, it _should_ seem, thinks
otherwise."--_W. Allen's Gram._, p. 65. "I _could_ wish you to go."--_Ib._,
p. 71. 3. WILL, &c. The following are nearly of the same character, but not
exactly: "The isle is full of noises; sometimes a thousand twanging
instruments _will_ hum about mine ears."--_Shak._ "In their evening sports
she _would_ steal in amongst them."--_Barbauld_.

"His listless length at noontide _would_ he stretch."--_Gray_.

OBS. 12.--As our old writers often formed the infinitive in _en_, so they
sometimes dropped the termination of the perfect participle. Hence we find,
in the infancy of the language, _done_ used for _do_, and _do_ for _done_;
and that by the same hand, with like changes in other verbs: as, "Thou
canst nothing _done_."--_Chaucer_. "As he was wont to _done_."--_Id._ "The
treson that to women hath be _do_."--_Id._ "For to _ben_ honourable and
free."--_Id._ "I am sworn to _holden_ it secre."--_Id._ "Our nature God
hath to him _unyte_."--_Douglas_. "None otherwise negligent than I you saie
haue I not _bee_."--_Id._ See _W. Allen's E. Gram._, p. 97.

"But netheless the thynge is _do_,
That fals god was soone _go_."--GOWER: _H. Tooke_, Vol. i, p. 376.

OBS. 13.--"_May_ is from the Anglo-Saxon, _maegan_, to be able. In the
parent language also, it is used as an auxiliary. It is exhibited by
Fortescue, as a principal verb; 'They shall _may_ do it:' i. e. they shall
be able (to) do it."--_W. Allen's Gram._,