procedo

A procedure: the deliberate way of going about something in order to reach a result. A surgical procedo, a manufacturing procedo, the procedo for renewing a passport. The verb procedi is to go about things in a particular manner, and it takes an adverb rather than an object: metode procedi, to proceed methodically.

Now untangle the trio, because Esperanto keeps three words where English blurs two.

• Procedo is the defined method. Somebody decided on these steps.
• Proceso at rank 1520 is the unfolding: a sequence of events happening over time, and in a courtroom the lawsuit itself. Juĝa proceso nails the legal sense when context will not.
• Procesio, landing in this same chapter, is a procession of people walking. Same Latin ancestor, entirely different word.

The test that separates the first two. If somebody wrote it down as instructions, it is a procedo. If it is simply happening, it is a proceso. Boiling water is a proceso; the recipe is a procedo. That distinction is sharper in Esperanto than in English, where "process" cheerfully does both jobs, and it is one of the small places where the planned language is genuinely tidier than the ones it borrowed from. Where you want the neutral word for a way of doing something with no ceremony attached, metodo is waiting at rank 1277.