leptotene
/ˈleptəʊtiːn/noun
mass noun
- Biology the first stage of the prophase of meiosis, during which each chromosome becomes visible as two fine threads (chromatids)【生】细线期（细胞减数分裂前期第一阶段, 其间每一个染色体显现为两条细线）。
词源
early 20th cent.: from LEPTO- 'narrow， fine' + Greek tainia 'band， ribbon'.