If the lower sign [of two hairs] appears before the upper sign [of the breasts] does, she can participate in chalitzah [the ceremony performed to release a widow of a childless man from the obligation of levirate marriage] or yibum [levirate marriage]. If the upper sign appears before the lower sign does, even though this is impossible, Rabbi Meir says: she does not participate in chalitzah or yibum. And the Sages say: she must participate in either chalitzah or yibum. For they have said: it is possible for the lower sign to appear before the upper sign has, but it is impossible for the upper sign to appear before the lower sign has.

Similarly, any earthenware vessel [with a hole] that lets [liquids] in will also let [liquids] out, but there is [such a vessel] that let [liquids] out but does not let [liquids] in. Any limb that has a nail also contains a bone [and is therefore considered a limb such that it renders the impurity of a corpse, even if it has less than the required measure of dead flesh to be able to render impurity], but there may be [a limb] that contains a bone but does not have a nail [and which would not be considered a limb for the purpose of rendering the impurity of a corpse, unless it contains the required measure of flesh to be able to render impurity].

Anything that can be rendered impure with midras impurity [a type of impurity due to being sat on by certain types of impure individuals, rendering something an Origin of impurity] can be rendered impure with the impurity of a corpse. But there may be something that can be rendered impure with the impurity of a corpse but cannot be rendered impure with midras impurity.

Anyone who is fit to [be a judge who may] try capital cases is also fit to try monetary cases. But there may be one who is fit to try monetary cases but is unfit to try capital cases. Anyone who is valid to serve as a judge is valid to testify. But there may be one who is valid to testify and is not valid to serve as a judge.

Any [food] that requires tithing can be rendered impure with the impurity of foods. But there may be [food] that can be rendered impure with the impurity of foods but which does not require tithing.

Any [crop] that requires pe'ah [the requirement to leave, when harvesting, a corner of the field for the poor] requires tithing. But there may be [a crop] that require tithing but which does not require pe'ah.

Any [livestock] that has the requirement of the first shearing [i.e. the obligation, when one shears one's sheep, to give a portion of the fleece to a priest] also has the requirement of the [priestly] gifts [i.e. when one slaughters an animal, the requirement to give certain portions of it to a priest]. But there may be [livestock] that has the requirement of the [priestly] gifts but does not have the requirement of the first shearing.

Any [produce] which is subject to [the obligation of] removal [i.e. the requirement to remove all of it from one's home during the sabbatical year once it is no longer available in the fields] is also subject to [the requirements of] the sabbatical year [i.e. one must give up ownership of its growing crop, and one cannot sell it for profit]. But there may be [produce] that is subject to [the requirements of] the sabbatical year but is not subject to [the obligation of] removal.

Any [fish] that has scales has fins. But there may be one which has fins but does not have scales. Any [animal] that has horns has [split] hooves. But there maybe be one which has [split] hooves but does not have horns.

Any [action] that requires a blessing after it requires a blessing before it. But there may be one that requires a blessing before it but does not require a blessing after it.

A female child who produced two [pubic] hairs may participate in either in chalitzah or yibum, and she is obligated in all of the commandments stated in the Torah. And similarly, a male child who produced two [pubic] hairs is obligated in all of the commandments stated in the Torah. And he is fit to become a wayward and rebellious son from the time he produces two hairs until his beard encircles; [this refers to] the lower [beard] and not the upper one, but the Sages spoke in a euphemism. A female child who has produced two hairs cannot do mi'un [the refusal of a marriage by a fatherless child married off by her mother or brother, retroactively annulling the marriage]. Rabbi Yehuda says: [she may still do mi'un] until the black [i.e. the hair] increases.

The two hairs spoken of regarding a red heifer [i.e. that two white or black hairs invalidate it, see, Parah 2:5], and [those spoken of] regarding nega'im [diseased patches on skin, clothes, or houses that create impurity; i.e. that two hairs on a blemish are a sign of impurity, see Nega'im 4:4], and regarding those spoken of anywhere, [the hairs must be long] enough to bent their tips to [touch] their roots, according to Rabbi Yishmael. Rabbi Eliezer says: [long] enough to be pinched by a finger-nail. Rabbi Akiva says: [long] enough to be removed with scissors.

Regarding a woman who saw a [blood] stain [on her clothing], she [with regarding to her counting of her days of impurity] is spoiled [i.e. she can no longer rely on her count], and she must take into consideration the possibility that there was a discharge [that day and the previous two days, rendering her a zavah and thereby impure for another seven days at least], according to Rabbi Meir. But the Sages say: [blood] stains do not contain discharge [and thus she need not suspect that she may be a zavah and therefore impure].

Regarding a woman who saw [a discharge of blood] on the eleventh day [i.e. her last day of counting, after which she should be pure] at twilight, or at the beginning of her being a niddah [a woman who has menstrual discharges which render her impure] and at the end of her being a niddah or at the beginning of the [subsequent] period of [potential] genital discharge and the end of that period of discharge [i.e. at twilight on what is either the first day of her being a niddah or the last day of the subsequent period of discharge during which she counts seven clean days, or at twilight on what is either the last day of her being a niddah or the first day of the subsequent period of potential discharge], or [if she saw blood] at the end of the fortieth day [after the birth] of a male, or at the end of the eightieth day [after the birth] of a female, at twilight in all these cases, they are thereby [assumed to be] mistaken [in their counting, and must therefore treat each case stringently]. Rabbi Yehoshua said: now that you have remedied [the situation for] the foolish women [who have mistaken their count], remedy [the situation for] the intelligent ones [who know how to count, as well, since they too may err in their counting].