Comma splice (or run-on sentences)

As Shaun Macleod explains in the video, a run-on sentence is a sentence that has two complete independent clauses, but no punctuation distinguishing one clause from the other.

A comma splice, however, occurs when two such clauses have been joined together with insufficient punctuation or joining words separating them. Students frequently join such sentences with a comma only (which is why they are known as a comma splice). The method you choose to fix a run-on sentence depends on the context and the meaning you intended.

Note: these examples demonstrate the problem of run-on sentences:
* We learned that song when we were in Ukestan,  an old man in a laundromat hummed it to us. * Note: Asterisks mean that this sentence is poorly constructed.

* The local team is looking confident heading into the game, the home team always has the advantage. *

* Marx claimed religion was the 'opiate of the masses', I consider television does a better job of stupefying people. *

* I got home late last night; I didn't have time for dinner. *

Grammarly has a nice explanation about comma splices in their blog.

1. Use a joining word.
   A comma splice can quickly be fixed using a comma with a joining word (conjunction).

Marx claimed religion was the opiate of the masses, but I consider that television does a better job of stupefying people. See Commas lesson 1

2. Use a semi-colon.
   A semi-colon is stronger than a comma and can serve to attach two independent clauses if the two clauses are closely linked by theme. (See Semicolons)

The local team is looking for confident heading into the game; the home team always has the advantage.

3. Use a full stop.
   Fixing a comma splice by making it into two sentences

We learned that song when we were in Ukestan. An old man in a laundromat hummed it to us.

4. Us a dependent clause marker
A comma splice can be fixed by making one of the sentences dependents on the other, such as starting with a word that turns it from an ordinary sentence to a dependent clause or using other grammatical changes to create the same effect.

Because I got home late last night, I didn't have time for dinner.

While Marx claimed religion was the opiate of the people, I consider that television is equally as effective at stupefying people.

The local team is looking for confident heading into the game, always having the advantage being on home turf.

Remember, the choice you make will depend on the meaning you wish to convey. For example, a conjunction signals a particular type of relationship between the ideas, so you would use it when you intend that relationship.