These words are from the IELTS 4000 Academic Word List and the sample sentences are taken from Cambridge free online dictionary.
accident: (noun) event that takes place without one's foresight or expectation; sudden, and unexpected event
She was injured in a car accident.
accidental: (adjective) unexpected; unforeseen
Reports suggest that eleven soldiers were killed by accidental fire from their own side.
accidentally: (adverb) inadvertently; by chance; casually; fortuitously; not essentially or intrinsically
He accidentally knocked a glass over.
accommodate: (verb) do a favor or service for; provide for; supply with; make suitable; adapt; allow for
New students may be accommodated in halls of residence.
accommodation: (noun) living quarters provided for public convenience
There's a shortage of cheap accommodation.
accompany: (verb) travel with; be associated with / to be provided or exist at the same time as something
The course books are accompanied by four CDs.
accomplish: (verb) succeed in doing; bring to pass; achieve; reach the end of; complete
The students accomplished the task in less than ten minutes.
accomplishment: (noun) achievement; fulfillment
Getting the two leaders to sign a peace treaty was his greatest accomplishment.
account: (noun)narrative or record of events; reason given for a particular action or event
She gave a thrilling account of her life in the jungle.
accountant: (noun) one who maintains and audits business accounts
The company is looking for an expert accountant.
accounting: system that provides quantitative information about finances
Please refer your query to the accounting firm.
accumulate: (verb) pile up; collect; mount up; increase
We've accumulated so much rubbish over the years.
accumulation: (noun) increase by natural growth or addition; concentration
Accumulations of sand can be formed by the action of waves on coastal beaches.
accuracy: (noun) quality of nearness to the truth or the true value
We can predict changes with a surprising degree of accuracy.
accurate: (adjective)capable of providing a correct reading or measurement; performing with care and precision
Her novel is an accurate reflection of life in Spain.
accusation: (noun) indictment; charge of wrongdoing that is made against a person or other party
He glared at me with an air of accusation.
accuse: (verb) blame; condemn
The surgeon was accused of negligence.
achieve: (verb) gain with effort; accomplish; fulfill
I've been working all day, but I feel as if I've achieved nothing.
achievement: (noun) feat; accomplishment; award for completing a particular task or meeting an objective
It gives you a sense of achievement if you actually make it to the end of a very long book.
acknowledge: (verb) declare to be true or admit; express obligation, thanks
Historians generally acknowledge her as a genius in her field.
acquire: (verb) gain through experience or effort; gain possession of; locate with tracking system
He acquired the firm in 2008.
acquisition: (noun) act of contracting or assuming or acquiring possession of something
The acquisition of huge amounts of data has helped our research enormously.
across: (preposition / adverb) from side to side; crosswise, or in a direction opposed to the length
She walked across the road. / When I reached the river, I simply swam across.
activate: (verb) make active or more active; stimulate; make radioactive
The alarm is activated by the lightest pressure.
actively: energetically; vigorously; in an active manner; voluntarily, not passively
He's very actively involved in the local party.
actual: (noun) true; real; being, existing, or acting at the present moment; current
We had estimated about 300 visitors, but the actual number was much higher.
actually: (adverb) truly; really; in fact
I didn't actually see her - I just heard her voice.
adapt: (verb) make fit for; change to suit a new purpose
Many software companies have adapted popular programs to the new operating system.
adaptation: modification; alteration or adjustment in structure or habits
Evolution occurs as a result of adaptation to new environments.
additional: (adjective) further; extra; supplemental or added to
There will be an extra charge for any additional passengers.
additive: (noun) addition; supplement
This margarine is full of additives – just look at the label!
address: (verb) make a formal speech to; deal with or discuss; direct efforts or attention of
He addressed a few introductory remarks to the audience.
adequate: (adjective) sufficient; enough to meet a purpose
I didn't have adequate time to prepare.