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When you have two complete sentences (subject + verb + object), you have several options for punctuating between them. The most common is the period.
However, there are two other easy options:
- a semicolon
- comma + conjunction
Thus, where you can use a period, you can technically use a semicolon OR a comma + conjunction. For our purposes, “CS” means “complete sentence” in the examples below.
Whereas CS = “Complete sentence,”
The reasons to use a semicolon instead of a period are varied, but most writers tend to use them in cause/effect moments. As well, you might be choosing to emphasize some sort of connection between the two ideas represented in the two sentences.
At any rate, the test for proper use is easy. If you are debating whether to use a semicolon, see if a period works in its place. If so, a semicolon is grammatically appropriate.
As for the last option, the comma + conjunction, this works as a set. You cannot have just a comma or just a conjunction. You must use both. Here is a list of conjunctions:
, and
, but
, or
, yet
Example (semicolon use)
Wrong
Lubricant viscous drag force develops on the cage surfaces resisting motion of the cage, as the cage rotates it creates centrifugal body forces, it then expands the cage outwards and tensile hoop stress is formed in the cage rails.
Right
Lubricant viscous drag force develops on the cage surfaces resisting motion of the cage; as the cage rotates it creates centrifugal body forces, it expands the cage outwards and tensile hoop stress is formed in the cage rails.
Example (semicolon use)
Wrong
Validation and verification of the simulation models is not something that is accomplished after the model is completed nor is it considered a single-application test, this should be carried out hand in hand with system development throughout the life cycle of the model.
Right
Validation and verification of the simulation models is not something that is accomplished after the model is completed nor is it considered a single-application test; this should be carried out hand in hand with system development throughout the life cycle of the model.
Example (comma + conjunction use)
Wrong
The pump is made primarily out of aluminum, but has some additional parts made out of PVC and steel.
Right
The pump is made primarily out of aluminum, but it has some additional parts made out of PVC and steel.
Example (comma use)
Wrong
The budget for this project has been analyzed as well, excluding engineering and other salaries, the project will cost US$25,123 to implement.
Right
The budget for this project has been analyzed as well; excluding engineering and other salaries, the project will cost US$25,123 to implement.