Verbal adjectives in English

It may seem pretty exotic to English-speakers that in some languages adjectives behave almost exactly like verbs, but this strategy is not as un-English as it looks. Consider the following colloquial American English sentences, with more formal approximate "translations":

This rocks! - This is good. (and not *This is rocking!)
That would rock! - That would be good.
That rocked! - That was good.
That was a rockin' day. - That was a good day.

This sucks! - This is bad. (and not *This is sucking!
That would suck! - That would be bad.
That sucked! - That was bad.
That was a sucky day. - That was a bad day.

In these, a property usually expressed with an adjective ("good", "bad") is being expressed using a stative verb, but only in predicative constructions (that is, to form a sentence.) In attributive function (that is, modifying a noun) an adjective derived from this verb is used. Like other stative verbs ("know", "be") but unlike non-stative verbs, it uses the simple present form to express a current situation, not the present continuous.

Within English, this pattern may seem pretty odd. But it corresponds rather well to how adjectives are expressed in Songhay languages, eg Koyra Chiini (Heath 1999:73). There, properties are expressed in predicative contexts just like verbs, with the same mood/aspect/negation particles, and in attributive contexts usually take a suffix:

ni beer - you are big (like ni koy - you went)
hal a ma beer - until it gets big (like a ma koy - he will go)
har beer - a big man

ni futu - you are bad
har futu-nte - a bad man

In Songhay the perfect aspect is used with stative verbs to express a current situation; but, like the English simple present tense, this is the simplest indicative verb form. The chief difference is that in Songhay the predicative verbs are used for inchoative senses too, as if "That rocks!" could mean "That is becoming good" as well as "That is good".

Typologically, I find it kind of interesting that what looks like a couple of verbal adjectives should be lurking in the recesses of the English lexicon. But it also has practical applications: if I were trying to teach Songhay or a typologically similar language to Americans, I would certainly start by discussing the example of these two English words.