Semi colons (;) are similar to colons, except where a colon is used to link directly related sentences, semi colons help separate independent ideas, or clauses. Another use of the semi-colon is to replace a period and sort a large list of items into distinguishable elements. To separate independent clauses:

 

 

Correct exampleIncorrect example
Our experiments show metabolomics is a novel tool in dietary analysis; to date, only two other studies have used similar methods.

Our experiments show metabolomics is a novel tool in dietary analysis: to date, only two other studies have used similar methods.

Incorrect because the second sentence does not provide additional details about the first sentence. Rather, it is new and different information, so a colon cannot be used.

Individual fitness depends on trade-offs among different environmental constraints; this in turn can restrict future range shifts.

Individual fitness depends on trade-offs among different environmental constraints: This in turn can restrict future range shifts.

Incorrect because the second sentence does not provide additional details about the first sentence. Rather, it is new and different information, so a colon cannot be used.

We can also use semi colons as a conjunction to replace a period. In academic writing, this is very useful because it can show a link between two sentences. In a long paragraph, this visual link can help the reader know which ideas are connected more closely.

 

Correct exampleIncorrect example
We used heart rate as a proxy for energy costs (overall dynamic body acceleration); however, this method still only indirectly approximates energy costs using previous data.

We used heart rate as a proxy for energy costs (overall dynamic body acceleration): however, this method still only indirectly approximates energy costs using previous data.

Incorrect because the second sentence is contradictory, rather than additional information. Therefore, a colon cannot be used as a conjunction.

RTK has some drawbacks, such as the effects of the troposphere and ionosphere, which result in systematic errors in the raw data; the distance between a rover (mobile) receiver and its reference (base) station has to be quite short (less than 10 km) in order to work efficiently.

RTK has some drawbacks, such as the effects of the troposphere and ionosphere, which result in systematic errors in the raw data: The distance between a rover (mobile) receiver and its reference (base) station has to be quite short (less than 10 km) in order to work efficiently.

Incorrect because a colon usually introduces material that must be directly related to the first sentence, so cannot be used as a conjunction.

To sort a large list of items into distinguishable elements:

 

Correct exampleIncorrect example
We categorized our experimental group into the following classes: fine-scale responses, including fast-twitch muscle use (Fig 1–A); cognition and memory capacity (Fig. 1–B); and physiological adaptation (Fig. 1–C).

We categorized our experimental group into the following classes: fine-scale responses, including fast-twitch muscle use (Fig 1–A), cognition and memory capacity (Fig. 1–B), and physiological adaptation (Fig. 1–C).

Incorrect because the first sentence introduces three elements, but the commas make it unclear whether they are indeed sub-elements of the first list element or are standalone elements.

The FOTUS model is the most parsimonious for two reasons: it incorporates sound statistical reasoning, but with fewer parameters than traditional approaches; and it’s the most viable of all three models owing to its low overheads.

The FOTUS model is the most parsimonious for two reasons: it incorporates sound statistical reasoning, but with fewer parameters than traditional approaches, and it’s the most viable of all three models owing to its low overheads.

Incorrect because the first sentence introduces two reasons, but the commas detract from where the reader should delineate these reasons from one another.

We had four professors on our committee: Peter Wursthorn, Professor of Mathematics; Ronald Pepin, Professor of English; Cynthia Greenblatt, Professor of Education; and Nada Light, Professor of Nursing.

We had four professors on our committee: Peter Wursthorn, Professor of Mathematics, Ronald Pepin, Professor of English, Cynthia Greenblatt, Professor of Education, and Nada Light, Professor of Nursing.

Incorrect because it is difficult to distinguish to which individual each title corresponds.

Note in the first example, without the semi colon, it is difficult to ascertain whether the elements in the list belong to the ‘classes’ or whether the last two elements (‘cognition and memory capacity’ and ‘physiological adaptation’) are sub-elements of the first element (‘fast-twitch muscle use’) in the list. The semi colons thus help distinguish separate the elements intro more digestible pieces. The advantage of using a semi colon as a tool to separate list items is being able to include more complete sentences as list elements with other punctuation, such as commas and parentheses.

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