الدلالة لغة هو الإرشاد
In ordinary language, dalālah means guidance.
كون الشيء بحيث يلزم من العلم به العلم بشيء آخر
A thing being such that knowing it entails knowing another thing.
The lexical definition highlights guidance; the technical definition describes the transition from one known thing to another. This need not involve speech. Seeing smoke and inferring fire is also a form of signification.