This is the 8435th most frequent French word.
acier
Steel.
In this sentence, 'acier' refers to the material of which the hammer is composed.
Le marteau est fait d'acier résistant.
The hammer is made of durable steel.
Here, 'acier' denotes the specific type of metal used in the engineering components of the bridge.
Les ponts modernes utilisent souvent des câbles d'acier pour leur structure.
Modern bridges often use steel cables for their structure.
In this context, 'acier' is used metaphorically to describe the strength and resilience of his heart.