Vaccine

a modified preparation of a VIRUS or BACTERIA that is no longer dangerous but can produce an immune response. It therefore gives immunity against infection with the actual disease. Vaccines can be administered by mouth or by a hypodermic syringe and are not effective immediately as it takes time for the recipient's IMMUNE SYSTEM to develop a memory for the modified virus or bacterium by producing specific ANTIBODIES.

Taken from Dictionary of Science

Factor

one of two or more quantities that produce a given quantity when multiplied together. For example, the factors of the number 8 are 1, 2, 4, 8.

Taken from Dictionary of Science

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Factors are the numbers you multiply together to get another number:

Example: 3 and 4 are factors of 12, because 3x4=12.

Also 2x6=12 so 2 and 6 are also factors of 12, and 1x12=12 so 1 and 12 are factors of 12 as well.

So ALL the possible factors of 12 are 1,2,3,4,6 and 12.

Taken from Math Is Fun?

Aberration

is what happens in physics when a lens (or curved mirror) does not produce a true image. It is caused by the light rays from any point on the object being viewed forming an image (focusing) at slightly different positions. In astronomy, aberration refers to the apparent change in position of a star. This is due to the fixed speed of light travelling from the star and the movement of the person looking at the star, because the Earth is moving in its orbit.

Taken from Dictionary of Science