zài / shù xué / zhōng / dìng xìng lǐ lùn / yán jiū / xì tǒng / zài / cān shù / biàn huà / xià / de / xíng wéi在数学中,定性理论研究系统在参数变化下的行为。In mathematics, qualitative theory studies the behavior of systems under parameter changes.