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

China has built up its presence in the Suez Canal region with a bilateral economic and trade cooperation zone. — Evelyn Cheng,priyanka Salve, CNBC, 31 Aug. 2026

She was admitted to Rhode Island Hospital with injuries that included bilateral internal carotid artery dissection, liver and spleen lacerations, multiple rib fractures, and a ruptured diaphragm. — Meg Walters, InStyle, 31 Aug. 2026

Last year, India finalized a new ten-year defense framework with the United States that deepens bilateral and regional security cooperation. — C. Raja Mohan, Foreign Affairs, 27 Aug. 2026

The Pakistani armed forces said the deal was signed by Kuwait’s defense minister during a visit to the garrison city of Rawalpindi focused on bilateral defense relations and security cooperation. — ABC News, 27 Aug. 2026

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