首先根据美国测量与材料协会（ASTM）颁布的ASTM D1566-07a标准，“Standard Terminology Relating to Rubber（橡胶相关标准术语学）”来辨析一下这两个词的定义及其涵盖范围。 rubber—material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, methyl ethyl ketone, or ethanol-toluene azeotrope. DISCUSSION—A rubber in its modified state, free of diluents, retracts within 1 min to less than 1.5 times its original length after being stretched at room temperature (18 to 29°C) to twice its length and held for 1 min before release. 以上就是该标准对于橡胶（rubber）的定义。从这个定义包含两层含义：（1）是说明了橡胶材料的力学特征——能够从大变形迅速而强烈的回复；（2）是说明了橡胶可以被改性（实际上就是化学交联）到不溶解、可溶胀的状态——能够被改性（或已经被改性）至一种不能被沸腾溶剂（如苯、甲基乙基酮、乙醇-甲苯共沸物）溶解（但可以溶涨）的状态。 该定义还对改性后的橡胶（不含稀释剂，可能是指增塑剂）的力学性能特点做了更明确的解释——在（18-29C）温度范围下被拉伸至本身原始长度的2倍并保持1min后撤出外力，能够在1min内回缩到小于其1.5倍原长。
