bilateral

adjective

bi·​lat·​er·​al (ˌ)bī-ˈla-t(ə-)rəl 

1

: affecting reciprocally two nations or parties

a bilateral treaty

a bilateral trade agreement

2

: having two sides

dealing with a bilateral problem

3

biology

a

: of, relating to, or affecting the right and left sides of the body or the right and left members of paired organs

bilateral nephrectomy

b

: having bilateral symmetry

bilateralism

(ˌ)bī-ˈla-t(ə-)rə-ˌli-zəm 

noun

bilaterally adverb

Did you know?

Since the prefix bi- means "two" in Latin, bilateral means essentially "two-sided". In the days when there were two superpowers, the U.S. and the Soviet Union regularly engaged in bilateral arms negotiations; such negotiations are much less common today. Sometimes bilateral refers to two sides of the same thing. A bilateral hip replacement, for instance, replaces both hip bones in the same operation. And bilateral symmetry (a term often used by biologists) refers to the fact that, in many organisms (such as humans), the left side is basically the mirror image of the right side.

Examples of bilateral in a Sentence

Recent Examples on the Web

Alongside the minerals deal, Xi reportedly agreed to purchase additional American soybeans and to strengthen enforcement against the export of chemical precursors used to produce fentanyl—long a major sticking point in bilateral talks. —Micah McCartney, MSNBC Newsweek, 30 Oct. 2025

The Comprehensive Test Ban Treaty from 1996 was never fully ratified, and Moscow suspended participation in the bilateral US-Russia New START deal in 2023, which will expire in February. —Tom Chivers, semafor.com, 30 Oct. 2025

On Tuesday, Transportation Secretary Sean Duffy revoked approval for 13 flight routes operated by Mexican airlines between the two countries for violating their bilateral aviation agreement signed in 2015. —Glenn Taylor, Sourcing Journal, 30 Oct. 2025

This means that bilateral trading volumes and financial flows will continue to dwindle. —Christopher Smart, Time, 29 Oct. 2025

Word History

First Known Use

1751, in the meaning defined at sense 1

Phrases Containing bilateral

• bilateral symmetry

Rhymes for bilateral

• collateral
• trilateral
• anterolateral
• posterolateral
• basolateral
• contralateral
• dorsolateral
• equilateral
• ipsilateral
• multilateral
• quadrilateral
• unilateral

Kids Definition

bilateral

adjective

bi·​lat·​er·​al (ˈ)bī-ˈlat-ə-rəl 

-ˈla-trəl

1

: having or involving two sides or parties

a bilateral treaty

2

: characterized by bilateral symmetry

bilaterally

-ē

adverb

Medical Definition

bilateral

adjective

bi·​lat·​er·​al (ˈ)bī-ˈlat-ə-rəl, -ˈla-trəl 

1

: of, relating to, or affecting the right and left sides of the body or the right and left members of paired organs

bilateral nephrectomy

bilateral tumors of the adrenal glands

2

: having bilateral symmetry

bilateralism

-ˌiz-əm 

noun

bilaterality

(ˈ)bī-ˌlat-ə-ˈral-ət-ē, -ˌla-ˈtral- 

noun

plural bilateralities

bilaterally

(ˈ)bī-ˈlat-ə-rə-lē, -ˈla-trə-lē 

adverb

Legal Definition

bilateral

adjective

bi·​lat·​er·​al ˌbī-ˈla-tə-rəl 

: affecting, obligating, or shared by both parties

bilaterally

-rə-lē

adverb