What is lanthanoid contraction & what ar the consequences of lanthanoid contraction?

Please refer to the given link:

https://www.meritnation.com/ask-answer/question/what-is-lanthanoid-and-actinoids-contraction/the-d-and-f-block-elements/1910852 

Consequences of the lanthanide contraction are:

1) Resemblance of second and third transition series

The pair of the elements: Zr-Hf, Nb-Ta, Mo-W etc. posses almost same size.

2) Similarity among lanthanide:

Because of the same change in the radii their chemical properties are quiet similar.

3) Basicity differences:

Basic strength of the hydroxides decreases with increases in the atomic number. La(OH)₃ is most basic while Lu(OH)₃ is least basic.