花序（inflorescence）是花梗上的一群、或一丛花，依固定的方式排列，是植物的固定特征之一。花序可以分为：无限花序和有限花序。

严格的说，花朵着生的分枝（stem）是种子植物的幼芽变异而来，包括节间和叶序（phylloaxis）在长度和性质上的变易，也包括主（main）花梗、次（secondary）花梗在比例（proportion）、压缩（compression）、膨大（swelling）、并生（adnation）、合生（connation）、退化（reduction）等处的变异。

支撑全部花序的分枝（stem），称为大（总、主）花梗（peduncle）；大花梗和花序内的其他分枝，称为脊梗（rachis，又称花轴）；支撑个别花朵的分枝，称为小（次）花梗（pedicel）。

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Morphologically, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified. The modifications can involve the length and the nature of the internodes and the phyllotaxis, as well as variations in the proportions, compressions, swellings, adnations, connations and reduction of main and secondary axes. Inflorescence can also be defined as the reproductive portion of a plant that bears a cluster of flowers in a specific pattern.