鉄は固い。
Words
鉄
(てつ)
iron (Fe); strong and hard (as iron); railway; railway enthusiast
は
(は)
topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis
硬い
(かたい)
hard; solid; tough; stiff; tight; wooden; unpolished (e.g. writing); strong; firm (not viscous or easily moved); safe; steady; honest; steadfast; obstinate; stubborn; bookish; formal; stuffy