The Greek word logos
(λόγος) is a singular masculine noun; its plural form is logoi
The range of meanings of the Greek logos is really daunting. In the Translator's Note to Klein's book she says it will be rendered as "reasonable speech; also: ratio" - which barely scratches the surface of the many different English terms often used to translate Greek logos, such as: word, story, account, reckoning, etc.
You can read the VERY VERY VERY LONG LSJ Greek-English dictionary entry online
for logos. It's fascinating to see all the different ways in which the word logos was part of Greek life and thought.
A related term is the adjective logistikos
(λογιστικός) and the noun logistike
(λογιστική), which Klein will call "logistic" or "logistical art" in English. You can read the LSJ Greek-English dictionary entry online
Another important word is the Greek verb logizesthai
(λογίζεσθαι), which I think will be rendered as "to calculate" in Klein's book. You can read the LSJ Greek-English dictionary entry online
Please add any questions and/or comments about this word and related words below.