Breakdown of В течение нескольких лет они изучали этот неизведанный океан.
они
they
этот
this [f: эта, n: это]
изучать
to study
год
year
Questions & Answers about В течение нескольких лет они изучали этот неизведанный океан.
Why does в течение end in -е instead of -и here?
В течение is a fixed compound preposition meaning 'over the course of' or 'during', and as a preposition of time, it always ends in -е. It takes the Genitive case, which is why we see нескольких лет right after it. This is a common spelling trap, as the literal noun phrase for 'in the current of a river' is spelled в течении in the Prepositional case.
Why does несколько change to нескольких in this sentence?
The word несколько (several) declines like a plural adjective in all oblique cases (any case other than Nominative or inanimate Accusative). Because the preposition в течение demands the Genitive case, несколько takes the Genitive plural adjective ending, becoming нескольких.
Why do we use лет for 'years' instead of a form of год?
The word год (year) has a highly irregular Genitive plural form: лет. This is historically the Genitive plural of лето (summer). Because нескольких is in the Genitive case, the noun it modifies must also be in the Genitive plural, so we use лет.
Why is the imperfective verb изучали used if the action took place over a completed period of years?