알아들었어요.

The Korean word '알아들었어요' (aradeureosseoyo) is a polite past tense form meaning 'I understood' or 'I comprehended.' It is a combination of several linguistic elements: * **알다 (alda):** This is the basic verb meaning 'to know,' 'to understand,' or 'to perceive.' It's an ancient Korean verb with cognates in other Altaic languages. * **아/어 들다 (a/eo deulda):** This is a compound verb construction. '들다 (deulda)' has multiple meanings, including 'to enter,' 'to take,' or 'to lift.' When combined with another verb using the connective '아/어,' it often adds a nuance of 'to take in,' 'to receive,' or 'to fully grasp' something. In this specific context, '알아들다' (aradeulda) means 'to take in and understand' or 'to comprehend.' The '들다' here emphasizes the internal processing and reception of information. * **-았/었- (-at/eot-):** This is the Korean past tense suffix. It indicates that the action of understanding has been completed. The choice between '-았-' and '-었-' depends on the vowel harmony of the preceding syllable. Since the stem of '알아들다' ends in '들' (whose vowel is 'ㅡ' which is usually followed by '-어' in some contexts, but here '들다' becomes '들었'), it takes the form '-었-' when followed by '-어요' or '-습니다.' So, '알아들다' becomes '알아들었-'. * **-어요 (-eoyo):** This is a common and polite informal ending for verbs in Korean. It is used in everyday conversation to express politeness to the listener without being overly formal. It indicates a statement or a question in a friendly manner. The choice between '-아요' and '-어요' also depends on vowel harmony. After the past tense suffix '-었-', it naturally combines to form '-었어요'. Therefore, '알아들었어요' literally breaks down to 'know-receive-past-polite informal ending,' conveying the meaning of having fully taken in and understood what was said. The construction 'verb + 들다' for comprehension is quite common in Korean, emphasizing the internal assimilation of knowledge or information.