Plural.
The antonym for "digraph" is "monograph." While a digraph is a combination of two letters representing a single sound, a monograph is a scholarly piece of writing on a specific subject.
Suite. I realize that only has five letters.
One possible word for a seal that is six letters is "marker."
The last six letters in the alphabet are U, V, W, X, Y, and Z.
French and Gallic are the names of two languages that are spelled with six letters. German and Polish also have 6 letters.
Singular.
An Antonym is a word meaning the opposite, for example the antonym of 'up' is 'down'. So the Antonym of 'singular' is 'plural'
whisper is the antonym of shout
Individual One Singular
An antonym for silent is loud, the antonym for silently is loudly, or aloud.
The adjective usage of the word Mock is defined as: fake or artificial. The antonym that has four letters is: Real
singular, one person
Cowardice
Delighted
Nothing
The singular possessive form of letter is letter's. The plural of letter is letters. The plural possessive of letters is letters'
opaque