DNA

DNA is a non-countable noun. This noun cannot be divided into discrete units or made plural. It requires the indefinite article some, an expression of quantity (a piece of, a lot of), or no article before it.

Non-countable Noun

We need DNA to conduct our sequencing experiments.

We acquired some DNA from an NIH laboratory.

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pipette

Pipette is a countable noun. This noun can be divided into discrete units. If the noun is singular, it usually requires the indefinite article a before it. If the noun is plural, it requires no article or some.

Singular Form of
Countable Noun		 Plural Form of
Countable Noun
A pipette was used to measure the volume.

Some pipettes were used to stir the mixture.

Pipettes were used to stir the mixture.

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gel

Gel is a countable noun. This noun can be divided into discrete units. If the noun is singular, it usually requires the indefinite article a. If the noun is plural, it requires no article or some.

Singular Form of
Countable Noun		 Plural Form of
Countable Noun
A gel was prepared to for electrophoresis.

Some gels were stored in the cold room.

Gels were prepared in advance.

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method

Method is a countable noun. This noun can be divided into discrete units. If the noun is singular, it usually requires the indefinite article a before it. If the noun is plural, it requires no article or some.

Singular Form of
Countable Noun		 Plural Form of
Countable Noun
A method to purify the compound was developed.

Some methods to purify the compound were too cumbersome.

Methods to draw blood from rabbits are not new.

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base pair

Base pair is a countable noun. This noun can be divided into discrete units. If the noun is singular, it usually requires the indefinite article a before it. If the noun is plural, it requires no article or some.

Singular Form of
Countable Noun		 Plural Form of
Countable Noun
A base pair is the basic unit of double-stranded DNA.

Some base pairs are unstable.

Base pairs are attracted through hydrogen bonding.

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protein

Protein can be either a non-countable or countable noun.

Example of "protein" as a Non-Countable Noun

Protein is essential to human nutrition.

Some protein, along with fat and carbohydrate, was essential for the survival of early hominids.

As shown above, the noun "protein" as a non-countable noun requires either the indefinite article some or no article before it.

Example of "protein" as a Singular Countable Noun

The protein hemoglobin was discovered early this century.

Example of "protein" as a Plural Countable Noun

Some proteins are resistant to trypsin digestion.

Proteins vary tremendously in size.

As shown above, the noun "protein" as a countable noun usually requires the article a if its is singular. In this case, we are referring to a specific protein--hemoglobin--so the definite article the is used. If the noun is plural, either the indefinite article some or no article is used.

Tip: To classify a noun as either countable or non-countable, it is often necessary to determine the meaning of the noun in the context of the sentence.

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yeast

Yeast is a non-countable noun. This noun cannot be divided into discrete units or made plural. It requires the indefinite article some, an expression of quantity (a piece of, a lot of), or no article before it.

Non-countable Noun

Yeast is necessary for baking bread.

We used some yeast in the fermentation process.

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software

Software is a non-countable noun. This noun cannot be divided into discrete units or made plural. It requires the indefinite article some, an expression of quantity (a piece of, a lot of), or no article before it.

Non-countable Noun

Software for the Macintosh computer is easy to use and learn.

The lab likes to use some software from Oxford Molecular Group for DNA sequence analysis.

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mathematics

Mathematics is a non-countable noun. This noun cannot be divided into discrete units or made plural. It requires the indefinite article some, an expression of quantity (a piece of, a lot of), or no article before it.

Non-countable Noun

Mathematics was a subject that she learned easily.

We all use some mathematics in our daily lives.

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sheep

Sheep is a non-countable noun. This noun cannot be divided into discrete units or made plural. It requires the indefinite article some, an expression of quantity (a piece of, a lot of), or no article before it.

Non-countable Noun

Sheep were recently cloned by a Scottish geneticist.

Some sheep from Whittle's lab were cloned from one sheep.

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