harder

词形变化：

动词过去式: hardened | 动词过去分词: hardened | 动词现在分词: hardening | 动词第三人称单数: hardens |

同义词：

strengthen | petrify | thicken | steel | cake | cohere | acclimate | solidify | freeze | set | consolidate | settle | coagulate | congeal | toughen | reinforce | stabilize | roughen | coarsen | indurate | inure | temper | season |

反义词：

soften |