思想 (sī xiǎng) is a compound noun meaning 'thought' or 'ideology', referring to the content, patterns, or systems of human thinking. While both characters individually mean 'to think' (思) and 'to imagine/think' (想), together they form a more abstract, formal term—often implying structured, reflective, or even philosophical mental activity. It frequently appears in academic, political, or literary contexts, such as 'Marxist thought' or 'creative thinking'.

Unlike everyday words like 想法 (xiǎngfǎ, 'idea') or 思考 (sīkǎo, 'to think'), 思想 carries weight and continuity—it suggests enduring beliefs, principles, or worldviews rather than fleeting mental images. It can be used both uncountably ('her political thought') and countably with measure words like 种 (zhǒng) or 体系 (tǐxì), as in 一种思想 ('a school of thought'). The word is neutral in tone but leans formal or serious, rarely appearing in casual speech about trivial matters.