Tending to produce dilation or expansion; having the effect of dilating or enlarging.
From dilate + -ive (adjective suffix). The -ive suffix indicates a tendency or inclination to produce a particular effect. Formation mirrors other -ative adjectives in English.
Heat is dilatative—it makes most materials expand, which is why bridges have expansion joints and power lines sag on hot days to prevent them from snapping in thermal stress.
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