What are other names for affirmation as a figure of speech?

As a rhetorical figure, affirmation has two real other names: affirmatio (Latin) and cataphasis (Greek). All three label the same move, positively asserting that something is the case. The shorter list is the catch: three nearby words get filed alongside them as synonyms and don't actually belong. Asseveration, asphalia, and the self-help sense of "positive affirmation" each name something different, and sorting them out is most of the work.

Affirmatio (the Latin name)

Affirmatio is the original Latin name for the figure. It comes from affirmare, "to make firm, to confirm," built from ad- ("to") plus firmare ("to strengthen"). The English noun affirmation is a direct anglicization of affirmatio. Same word, same figure, one language layer removed.

In the classical tradition, affirmatio is the headword. Quintilian uses it in the Institutio Oratoria (9.2) when discussing how a speaker drives a point home by asserting it plainly rather than arguing it. When a glossary or reference work lists the figure under one canonical name, that name is almost always affirmatio, paired against negatio in the classical affirm/deny opposition.

Cataphasis (the Greek name)

Cataphasis (Greek kataphasis, "affirmation, assertion"; pronounced ka-TAPH-a-sis) is the Greek doublet. It pairs against apophasis, "denial," and the cataphasis/apophasis opposition is the classical Greek frame for the affirm/deny split. English rhetorical handbooks often prefer the Latin pair (affirmatio/negatio) when teaching the figure, but both pairs name the same opposition.

Reach for cataphasis when the argument is explicitly Greek-flavored, when apophasis is already on the page, or when the pairing is doing structural work and the Greek terms keep the symmetry. In any other context, affirmation (English) or affirmatio (Latin) reads more cleanly.

Words that look like synonyms but aren't

Three terms read like synonyms for affirmation and aren't. None of them name the same figure.

Term	What it actually names	Why it's not a synonym
Asseveration	An earnest, solemn declaration, usually backed by an oath or strong assurance.	Narrower than affirmation. Every asseveration is an affirmation, but most affirmations aren't asseverations. The figure is about plain positive assertion, not about the force or solemnity of the speaker's commitment.
Asphalia	The figure where a speaker offers themselves as surety or guarantor for a claim ("I stake my reputation on this").	Adjacent but distinct. Asphalia is about pledging, putting the speaker's standing behind the claim. Affirmation is about asserting, naming the thing as true. The speaker's stake is optional, not constitutive.
"Positive affirmation" (self-help)	A repeated motivational statement spoken to oneself ("I am enough").	Same English word, different concept. It's a self-talk practice from 20th-century psychology, not a named figure in the rhetorical tradition. The two senses share a noun, not a referent.

The quick test: if you can replace the word with positive assertion and the meaning holds, you're on the figure. If you'd have to replace it with sworn declaration, self-guarantee, or motivational mantra, you've drifted into a neighbor.

Which name to use when

In running English prose, use affirmation. It's the natural word, and the rhetorical sense lands clearly enough in context. Move to affirmatio when the article is explicitly Latin-flavored or when listing the figure under its canonical classical headword. Move to cataphasis when the apophasis pair is structurally present, or when the discussion is anchored in Greek rhetoric.

For glossaries and reference entries, affirmatio is the canonical headword in the classical tradition, and that's where the substance of the figure belongs. The other two names are pointers to it.