# Abstract Contracts * * Contracts must be marked as abstract when at least one of their functions is not implemented or when they do not provide arguments for all of their base contract constructors * Even if this is not the case, a contract may still be marked abstract, such as when you do not intend for the contract to be created directly * Abstract contracts are similar to Interfaces but an interface is more limited in what it can declare.
* An abstract contract is declared using the abstract keyword as shown in the following example * Note that this contract needs to be defined as abstract, because the function utterance() is declared, but no implementation was provided (no implementation body { } was given) ```solidity // SPDX-License-Identifier: MIT pragma solidity ^0.8.0; abstract contract Fruit { function color() public pure virtual returns (bytes32); } contract Apple is Fruit { function color() public pure override returns (bytes32) { return "green"; } } ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.eridian.xyz/ethereum-dev/solidity-notes/abstract-contracts.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.