思虑 (sī lǜ) is a formal, literary noun meaning 'thought', 'reflection', or 'careful consideration'. It combines the characters 思 (sī), meaning 'to think' or 'to reflect', and 虑 (lǜ), meaning 'to consider' or 'to worry about'; together they emphasize deliberate, often deep or anxious mental activity. Unlike the more neutral word 想法 (xiǎngfǎ, 'idea') or 思考 (sīkǎo, 'thinking' as a verb), 思虑 carries a subtle connotation of seriousness, concern, or mental burden — it’s commonly used when describing prolonged, weighty contemplation, especially about important decisions or troubling matters.

This word appears frequently in written Chinese — such as essays, news reports, or classical-style expressions — and less often in casual speech. It’s often modified by adjectives like 深重 (shēnzhòng, 'profound'), 过度 (guòdù, 'excessive'), or 长期 (chángqī, 'long-term'), and may appear in phrases like 思虑过多 ('overthinking') or 思虑周全 ('thorough consideration'). It can also function as a subject or object in sentences, but rarely as a verb.