Parallelism refers to the principle that parts of a sentence that are the same in function should be the same in structure. Words or phrases joined by coordinating conjunctions should have the same form.
When NASA first organized the Viking Lander missions to Mars, one of the
most vexing problems its scientists faced was devising and
agreeing upon tests to detect life.
--Kai Wu, "Artificial Life," SciTech Magazine.
Make sure phrases joined by coordinating or correlative conjunctions are parallel. All phrases must be of the same type.
An important consideration in orthopedic surgery and how to implant prostheses is the possibility
of infection.
An important consideration in orthopedic surgery and prosthesis implants is the possibility of infection.
--Linglei Xu, "Bone Talk," SciTech Magazine (modified)
Make sure all items or phrases in lists are parallel.
The comparison will cover
- possible mechanisms of change [noun phrase]
- how the fissures widen because of regional tectonic stress [noun
clause]
- are there changes in permeability from increased microcracking?
[question]
The comparison will cover
- possible mechanisms of change [noun phrase]
- fissure widening from regional tectonic stress [noun phrase]
- permeability from increased microcracking [noun phrase]
Make sure all headings and subheadings are parallel with the other headings and subheadings of the same level.
Make sure all entries of the same level in an outline are parallel.
3 Strategies for developing tooling systems for high- speed machining 3.1 How chemically stable materials are made [noun clause] 3.2 Diffusion-limited wear regimes [noun phrase] 3.3 Isolate the tool from the workplace [imperative]
3 Strategies for developing tooling systems for high-speed machining 3.1 Chemically stable materials [noun phrase] 3.2 Diffusion-limited wear regimes [noun phrase] 3.3 Isolation of the tool from the workplace [noun phrase]
See also Nonparallel Comparisons.