On the Internet, every computer that can be reached over the network is commonly known as a ________.

Introduction / Context:
The Internet connects many types of devices: personal computers, servers, routers, phones and more. In networking terminology, any device that has an IP address and can participate directly in network communication is given a generic name. This question asks you to recall that general term for a computer on the Internet, regardless of whether it is acting as a client or a server in a particular communication.

Given Data / Assumptions:

• We are talking about computers connected to the Internet.
• Each such computer has an IP address and can send or receive data.
• The role may be client, server or both, depending on the application.
• Options include client, modem, server, host and router.

Concept / Approach:
In IP networking, any device that has an IP address and can send and receive packets is called a host. The term is neutral with respect to the device's specific role. When a host initiates a request, we informally call it a client; when it responds to requests or offers services, we call it a server. A single machine can act as both client and server at different times. A modem is a communication device that connects a local network or single computer to an Internet service provider; it is not itself the generic name for every Internet connected computer. Therefore, the correct term for every computer on the Internet is host.

Step-by-Step Solution:

Verification / Alternative check:
Networking textbooks and RFC documents frequently use the word host when referring to endpoints in an IP network. For example, they speak of host A sending packets to host B. Diagrams label end computers as hosts while routers are drawn separately as intermediate devices. Client and server roles are usually described in the context of specific application protocols such as HTTP or FTP. ISP documentation describes modems and routers as equipment connecting hosts to the Internet, not as hosts themselves in most contexts. All of this reinforces the idea that host is the generic term for every Internet connected computer.

Why Other Options Are Wrong:

• Client: Refers to a host that requests services in a particular client server interaction, not to every Internet computer generically.
• Modem: A device that modulates and demodulates signals to connect one or more hosts to an ISP; it is not the name for all Internet computers.
• Server: Refers to a host that provides services; many Internet computers act only as clients.
• Router only: Routers are special network devices that forward packets; many Internet hosts are not routers.

Common Pitfalls:
Some learners think of client or server as the default term for any Internet computer because they hear these words often in web contexts. However, these are role specific terms. Another confusion is to focus on the modem or Wi-Fi router in a home network and assume it is the main Internet device; while important, it is not the generic name for all connected machines. To answer questions correctly, remember that the neutral term for any device with an IP address participating on the network is host.

Final Answer:
Every computer on the Internet is commonly known as a Host.