深究 literally combines 深 (shēn, 'deep') and 究 (jiū, 'to investigate or examine thoroughly'), forming a verb meaning 'to investigate thoroughly' or 'to probe deeply into something.' It implies going beyond surface-level understanding to uncover root causes, underlying principles, or hidden details. The word carries a formal, somewhat academic or analytical tone — it's commonly used in contexts like scientific research, medical diagnosis, legal inquiry, or critical thinking.

While 深究 can be applied to any complex issue, it often appears in serious or professional settings where rigorous analysis is expected — for example, when doctors deep-dive into the cause of a rare symptom, or when journalists trace the origins of misinformation. It’s rarely used in casual conversation; instead, it signals deliberate, methodical scrutiny. Note that it's almost always transitive and typically followed by a noun phrase (e.g., 深究原因, 深究细节) or introduced with the particle '对' (e.g., 对问题深究).