What does "cons" mean?

1. (disadvantages) the negative points or disadvantages of an idea or plan. 2. (programming data structure) a basic building block in some computer languages used to hold two pieces of data together. 3. (to add to a list) to add a new item to the beginning of a list in computer programming.

How do you use "cons"?

The verb is transitive and typically takes the element being added as the object.

cons

n. · v.

US //ˈkɑnz// UK //kˈɒnz// cons

1 disadvantages (n.)
B1 Intermediate

the negative points or disadvantages of an idea or plan.

the arguments or factors against a particular proposition or course of action.

Example

We need to weigh the pros and cons before we decide to move house.

Example

The committee spent hours debating the pros and cons of the proposed merger, focusing specifically on long-term financial stability.
- pros
2 programming data structure (n.)
C2 Proficiency Technical Computing

a basic building block in some computer languages used to hold two pieces of data together.

a fundamental data structure in Lisp and related functional languages, consisting of a pair of pointers (traditionally car and cdr).

Example

In Lisp, a list is actually a series of cons cells linked together.

Example

The function returns a new cons whose first element is the input value and whose second element is the existing list.
- pair
- cell
3 to add to a list (v.)
C2 Proficiency Technical Computing

to add a new item to the beginning of a list in computer programming.

to prepend an element to a list by creating a new cons cell; the standard method of list construction in functional programming.

Example

You can cons the new ID onto the front of the user list.

Example

The algorithm efficiently conses each discovered node onto the accumulator to build the result set in linear time.

Usage

The verb is transitive and typically takes the element being added as the object.
- prepend
- attach

Related words

Last updated June 20, 2026