Mostly during download from the internet, a variable download speed is observed todiscuss the phenomena considering delays.

The variable download speed observed during internet downloads can be attributed to several factors, including but not limited to:

1. Network Congestion: This is the most common cause of variable download speeds. When too many people are accessing the same network resources, it can cause the speed to decrease. This is often the case during peak usage times, such as in the evening when many people are home from work and online.

2. Server Load: The speed of your download can also be affected by the server from which you're downloading. If the server is under heavy load, it may not be able to send data as quickly, resulting in slower download speeds.

3. Physical Distance: The further away you are from the server you're downloading from, the longer it takes for data to be transferred. This is due to the time it takes for data to travel, or latency.

4. Quality of Connection: The quality of your internet connection can also affect download speeds. This includes factors such as how strong your Wi-Fi signal is, whether your connection is wired or wireless, and the quality of your internet service provider's network.

5. Computer Performance: If your computer is running other heavy applications at the same time, it might not be able to process the incoming data as quickly. This can result in slower download speeds.

6. Throttling: Some Internet Service Providers (ISPs) may limit your download speeds at certain times of day, or after you've downloaded a large amount of data. This is known as throttling.

In conclusion, the variable download speed is a complex phenomenon influenced by a multitude of factors. It's not just about the speed of your internet connection, but also about the load on the server you're downloading from, the distance between you and the server, the quality of your connection, and the performance of your computer.