do something" (the so-called conative imperfect ); hence the same verb, in the imperfective (present or imperfect) and aorist, respectively, is used to convey look and see , search and find , listen and hear . (For example, ηκουομεν ēkouomen "we listened" vs. ηκουσαμεν ēkousamen "we heard".) Spanish has similar pairs for certain verbs, such as (imperfect and preterite, respectively) sabía "I knew" vs. supe "I found out", podía "I was able to" vs. pude "I succeeded (in doing something)", quería "I wanted to" vs. quise "I tried to", no quería "I did not want to" vs. no quise "I refused (to do something)". Such differences are often highly language-specific. The English tense–aspect system has two morphologically distinct tenses, present and past. No marker of a future tense exists on the verb in English; the futurity of an event may be expressed through the use of the auxiliary verbs " will " and " shall ", by a present form plus an adverb , as in "tomorrow we go to New York City", or by some other means. Past is distinguished from present–future, in contrast, with internal modifications of the verb. These two tenses may be modified further for progressive aspect (also called continuous aspect), for the perfect , or for both. These two aspectual forms are also referred to as BE +ING [ 8 ] and HAVE +EN, [ 9 ] respectively, which avoids what may be unfamiliar terminology. (While many elementary discussions of English grammar classify the present