English: It's all about the Ones.

Our entire numbering system is set up to count ones. The Ones column is at the center of the place-value naming system. It is the axis of symmetry.

Decimal names reflect whole number names. Hundredths on the right is Hundreds on the left with "th" inserted. Fractions use the same "th" ending: fourth, fifth.

Columns to the left of the Ones column count complete ones.

Columns to the right of the Ones column count pieces of one.

While the digits on the left can count millions of ones, all the decimal digits on the right zoom in to describe part of one single, sliced-up one.

Decimals use place value to provide the information that's in the denominator of a fraction. Efficient, but decimals can only specify 10-splits. Split by 10, again and again and again. Tenths, hundredths, thousandths...

Fractions can split 1 into any number of equal parts: thirds, fourths, fifths... even tenths.

Note the first decimal piece is a tenth, not the mythical "oneth." The decimal point is but a dot at the foot of the Ones column. It marks the start of the other method for representing fractional pieces.