Mandarin · Chapter 18 · Lesson 5 · Grammar primer
The double 了 sentence
我学了三年中文了 (I have been studying Chinese for three years now). The verb-了 closes off a measured chunk of action; the sentence-final 了 says it is still going at the moment of speaking. Drop the final 了 and the three years are over; drop the verb-了 and the duration loses its anchor.
The lesson is a long-form read rather than a flashcard session. Open the primer below, work through it once, then come back and continue with the next lesson.
Read the primer