In older forms of English, a distinction was made between yea /jei/ and nay /nei/ and yes and no, the former two being used when the preceding statement contained no negative, the latter two being used when the preceding statement did contain a negative: “Myn hertes greef, mote I not wepe? – O yis.” (SOED: 2589) In this function, yes is comparable to German doch, French si or Swedish jo. The distinction became generally obsolete after 1600. It is remarkable that the “normal” form has disappeared. The “stronger”, the more emphatic form has survived. It is also remarkable that German, French and Swedish do not have a form which corresponds to no in the old sense, although they have one that corresponds to yes in the old sense.