Generic sentences (e.g., “birds lay eggs”) express generalizations about kinds, in contrast to non-generic sentences that express facts about specific individuals or sets of individuals (e.g., “all birds lay eggs”). Although generics are pervasive in natural language, there is no unique linguistic marker of genericity, making the identification of generics a challenge. We investigate the morphosyntactic cues that listeners use to identify whether a sentence should receive a generic interpretation or not. We find that two factors – the definiteness of a sentence’s subject NP and the tense of the sentence – are extremely important in guiding intuitions about whether a sentence should receive a generic interpretation. We argue that the importance of these factors can be explained by taking generic interpretations to arise due to a failure to ground expressions as referring to specific entities or events.