English Reference
verb

strengthen

v.
US /ˈstɹɛŋθən/ UK /stɹˈɛŋθən/ strength·en UK spelling strengthened, strengthens

  1. 01 B1 Intermediate

    to make something tougher or more solid so it does not break.

    to increase the physical power, durability, or structural integrity of an object or body part.

    Simple

    You can do these exercises every morning to strengthen your back muscles.

    In context

    The engineers decided to strengthen the bridge's support pillars with carbon fibre to ensure they could withstand the increased weight of modern traffic.

    Usage

    Often used with a direct object representing a body part or a physical structure.

    weakenenfeeble
  2. 02 B2 Upper Intermediate

    to grow in power or intensity.

    to increase in force, intensity, or power; used without a direct object.

    Simple

    The wind began to strengthen as the storm moved closer to the coast.

    In context

    Economic indicators suggest that the local currency will continue to strengthen against the dollar throughout the next fiscal quarter.

    Usage

    Intransitive use; the subject is often a natural force, a currency, or an abstract trend.

  3. 03 B2 Upper Intermediate

    to make an idea or a feeling more certain or powerful.

    to provide additional evidence or support to an argument, belief, or emotional state.

    Simple

    The new evidence will strengthen our case in court tomorrow.

    In context

    The latest archaeological findings significantly strengthen the theory that the ancient settlement was a major trading hub rather than a simple military outpost.

  4. 04 B2 Upper Intermediate

    to make a connection between people or a position in a group more secure.

    to consolidate or improve the quality of a relationship, alliance, or strategic position.

    Simple

    The two countries signed a new treaty to strengthen their friendship.

    In context

    The CEO's recent keynote address was designed to strengthen investor confidence following a period of significant market volatility.

Usage strengthen social · strengthen security · strengthen argument

Turkiye would also continue to strengthen ties with Kurdish communities and safeguard their rights across the region, he added.

Al Jazeera· 15 Aug 2026

It also strengthens immune defences and repairs muscle tissue.

BBC News· 19 Jul 2026

From rare Middle English strengthenen (14th c.), from earlier strengthen (12th c.), where -en is the infinitive ending. Probably the original form was reinterpreted as strength + -en around the time when the infinitive ending was being apocopated in late Middle English.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Middle English strengthenen
Level B2 · Upper Intermediate
Frequency Common
Updated