Latin lacks the following features:
- Dual number. See Allen & Greenough, New Latin Grammar § 134.a, note 1.
- Present passive participle (Allen & Greenough § 492).
- Perfect active participle, except for deponent verbs (Allen & Greenough § 493).
- Words for yes and no (Allen & Greenough § 336: "There is no one Latin word in common use meaning simply yes or no."). On ways around this lack, see H. Thesleff, Yes and No in Plautus and Terence (Helsinki, 1960) = Societas Scientiarum Fennica. Commentationes humanarum litterarum, XXVI, 3.
- Definite and indefinite articles.
The list could be expanded.