Refers to the physical property of being hard, often used in technical or descriptive contexts.
The hardness of this material rivals that of diamond.
firm; strong; hard-line; uncompromising
hardening; stiffening; solidifying · hardening (of attitude); stiffening; toughening · upturn (in the market); firming up
hard type; hardball; hard (tennis)
stiffening; rigidity; ossification
hard-liners; diehards; hawks · tough guy; man's man; traditionally masculine man · hard news; political/economic reporter · strait-laced; conservative in relationships · bullish traders
hardness; solidity
hardness; stiffness; rigidity
cirrhosis of the liver; hepatic cirrhosis
hard water
pen or pencil; hard-tipped writing implement
hardness and softness; hard line and moderate line
hardness
hard ball; regulation ball
crude; immature; unpolished
hard ticket; cardboard ticket
cirrhosis
hardwood
hardwood
terminal hair; bristle
jadeite
hardpan
induration; hardening
plaster; adhesive plaster; medical plaster
The kanji 硬 means 'hard' and is used in compounds. The reading こう is the on'yomi.