What is the difference between a feasibility study and pre-feasibility study?

According to Guidelines for Grant Applicants Part 3: Glossary.
(No 28) Feasibility study: an investigation which tries to clearly establish whether a project will work and achieve its expected results. Such a study usually evaluates in detail a project's technical design, its costs and benefits, social and environmental aspects, institutional issues, financial aspects, feasibility of investments, etc. Feasibility studies are usually carried-out in the preparation stage of the project cycle.
(No 46) Pre-feasibility study: preliminary assessment of viability of the action that usually takes place in the identification stage of the project cycle. Pre-feasibility studies generally cover the same subjects as feasibility studies, but do so in much less detail.