The technical field of the invention or utility model should be the specific technical field to which the technical scheme of the claimed invention or utility model belongs or is directly applied, not the superior or adjacent technical field, nor the invention or utility model itself.

This particular technical field is often related to the lowest possible position of an invention or utility model in the international patent classification table.

For example, an invention about an excavator cantilever is improved by changing the rectangular cantilever section in the background technology into an elliptical section. Its technical field can be written as "the invention relates to an excavator, in particular to an excavator cantilever" (specific technical field), but it is not suitable to be written as "the invention relates to a construction machine" (upper technical field) or "the invention relates to an elliptical section of an excavator cantilever" (the invention itself).