Key Difference: The word dongle is used in many contexts. Generally, it refers to a device which is connected to the computer in order to control access to a particular application like software, etc. Modem stands for Modulator/Demodulator.  It is a networking device that is used for converting analog and digital data used in communication between computers. In simple words, it provides access to the internet. Commonly, wireless USB modems are also referred to as dongles. These dongles act as modems by enabling the PCs or laptops to connect wirelessly to the internet, and therefore they are also termed as USB modems.

The word dongle is used in many contexts. It refers to a device which is connected to the computer in order to control access to a particular application like software, etc. Dongle was originally used in context to devices which were used to enable running of a particular software program. This reduces the chances of unauthorized uses. However, the word dongle is being used in many contexts now. For example- in networking it refers to a short network cable adapter.

The most common usage of dongle is in context to a USB dongle, which provides the connectivity to the internet. Dongles therefore include wireless modems, software copy protect devices and adapters. A WiFi dongle is 802.11g USB adapter which provides access to a wireless network.

Modem stands for Modulator/Demodulator.  It is a networking device that is used for converting analog and digital data used in communication between computers. In simple words, it provides access to the internet. Depending on the types of internet connection, modems can be divided into cable modems, DSL and Dial-up modems.

Commonly, wireless USB modems are also referred to as dongles. These dongles act as modems by enabling the PCs or laptops to connect wirelessly to the internet, and therefore they are also termed as USB modems.

Comparison between Dongle and Modem:

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