Can we say node.js is a web server?

Web server

Web server can refer to either the hardware (the computer) or the
software (the computer application) that helps to deliver content that
can be accessed through the Internet.1

The primary function of a web server is to deliver web pages on the
request to clients. This means delivery of HTML documents and any
additional content that may be included by a document, such as images,
style sheets and scripts.

A web server is the basic to delivering requests/pagess to the clients/user on the internet

Web framework

A web application framework is a software framework that is designed
to support the development of dynamic websites, web applications and
web services. The framework aims to alleviate the overhead associated
with common activities performed in Web development. For example, many
frameworks provide libraries for database access, templating
frameworks and session management, and they often promote code reuse.

A web framework uses a webserver to deliver the requests to client, but it is not the web server.

Node.js

Node.js is a platform built on Chrome’s JavaScript runtime for easily
building fast, scalable network applications. Node.js uses an
event-driven, non-blocking I/O model that makes it lightweight and
efficient, perfect for data-intensive real-time applications that run
across distributed devices.

But then again you can also create CLI apps so I think you should see it more as a platform to write javascript programs to run on your server(computer) using Javascript programming language instead of just in the browser as in the beginning. I think you could see it as Javascript++ ??

You can also write web server with node.js as you can see on the front page of node.js. In the beginning Ryan said you could put Nginx in front of node.js because of the stabilty of the project. The project was and still is pretty young. Nginx is a proven web server that will keep on running while node.js can crash. Then again a lot of user just use node.js for that.