mood in English

English has one inflected form that does nothing but mark a non-factual stance, and it belongs to one verb. In a counterfactual conditional the verb be appears as were in the first and third person singular, where the ordinary past would be was, and the choice between the two is the choice between a hypothetical reading and a factual one. No other verb in the language has such a form. That single cell is why this record reads explicit rather than periphrastic, and it should be read for what it is: a residue, not a paradigm.

Two further constructions do part of the work without an inflection of their own. In a complement clause after a verb of demanding or proposing, the verb appears in its plain form regardless of the tense of the main clause and regardless of the person of its own subject, so it fails to take the ending it would otherwise be required to take. Whether that is a distinct inflected form or the absence of one is exactly what the dispute is about. The imperative uses the same plain form with no subject expressed, and is either a third construction or the same one again depending on the analysis chosen.

Everything else is carried by the modal auxiliaries. That class is closed, its members take no ending at all, they do not stack, they invert and negate like auxiliaries rather than like verbs, and they cover possibility, obligation, ability, permission and prediction between them. A language with a full mood paradigm distributes those meanings across inflected forms of every verb; English concentrates them in about nine words that are defective in every direction.

The record is contested because the two standard analyses disagree about whether the language has a subjunctive at all. On one, the plain form in the demanding complement is a subjunctive inflection and were is a second one, giving a small but genuine paradigm. On the other, there is no subjunctive form, only a construction that selects the plain form, and were is an isolated irrealis relic. The convention adopted here treats were as the single inflected exponent and the complement pattern as a construction, and it is recorded as a convention. The obligatoriness is conditioned because the marking appears only in a stated set of environments and nowhere else.