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4.3 Terminology

The important terms used in dimensioning are :

Figure 4.7 : Dimension terminology

the numerical value that defines the size or geometric
Dimension -
characteristic of a feature

the numerical value defining the theoretically exact size of a
Basic dimension -
feature

Reference the numerical value enclosed in parentheses is provided for
-
dimension information only and is not in the fabrication of the part

the thin solid line which shows the extent and direction of a
Dimension line -
dimension

are placed at the ends of dimension lines to show the limits of the
Arrows -
dimension

the thin solid line perpendicular to a dimension line indicating
Extension line -
which feature is associated with the dimension

The thin solid line used to indicate the feature with a dimension,
Leader line -
note or symbol is associated

Tolerance - The amount of a particular dimension is allowed to vary