factor

important, main, major, relevant, significant

Good weather was an important factor in making the trip successful.

critical, crucial, deciding, decisive, determining, key, vital

Good communication was a key factor in making their relationship work.

contributing, contributory

Lack of sleep was a contributing factor in why she failed the test.

complicating, distorting

Budget cuts have become a distorting factor in how fairly the school system treats all students.

mitigating

His lawyer presented several mitigating factors that convinced the judge to reduce his sentence.

single

Lack of sleep was the single biggest factor affecting her performance at work.

common

The lack of sleep was a common factor in why so many students failed the exam.

external, extraneous, extrinsic

Weather and economic conditions are external factors that affected the company's sales this year.

risk

Poor sleep is an important risk factor in developing heart disease.

consider, take into account

When choosing a school, parents must consider many important factors.

be involved, operate

Several important factors were involved in their decision to move abroad.

affect sth, be responsible for sth, contribute to sth, determine sth, influence sth, precipitate sth, predispose sb/sth to sth

Several factors contributed to the company's decision to relocate their offices downtown.

constrain sth, inhibit sth, militate against sth

Several important factors constrained the project's budget this year.

interact

Several factors interact to determine whether a student succeeds in school.

~ behind

The reasons behind their decision to move abroad surprised everyone in the family.

~ in

Weather was an important factor in choosing where to build the new school.

a combination/number/range/variety of factors

Success in learning a language involves a combination of practice, motivation, and good teaching.