monocotyledon
noun [ C ] biology specialized uk/ˌmɒn.əʊˌkɒt.ɪˈliː.dən/ us/ˌmɑː.nəˌkɑː.təlˈiː.dən/
单子叶植物（一种开花植物，种子内部只有一片子叶，如水仙、草等）
a type of plant that produces flowers and has only one cotyledon (= leaf part inside the seed). Monocotyledons include daffodils and grasses.