Mishnah Taharos 2:2: Rabbi Eliezer says: One who eats foods of a first degree [level of impurity] is [himself rendered] of a first degree; [if he eats] foods of a second degree, [he is rendered] of a second degree; foods of a third degree, [he is rendered] of a third degree. Rabbi Yehoshua says: One who eats foods of a first degree or of a second degree is [rendered] of a second degree; [one who eats foods] of a third degree, [he is rendered] of second degree for sanctified foods, but not for terumah, [and this applies] with non-sacred food prepared with the purity stringency of terumah [since regular non-sacred foods do not have third degree impurity].

רַבִּי אֱלִיעֶזֶר אוֹמֵר, הָאוֹכֵל אֹכֶל רִאשׁוֹן, רִאשׁוֹן. אֹכֶל שֵׁנִי, שֵׁנִי. אֹכֶל שְׁלִישִׁי, שְׁלִישִׁי. רַבִּי יְהוֹשֻׁעַ אוֹמֵר, הָאוֹכֵל אֹכֶל רִאשׁוֹן וְאֹכֶל שֵׁנִי, שֵׁנִי. שְׁלִישִׁי, שֵׁנִי לַקֹּדֶשׁ וְלֹא שֵׁנִי לַתְּרוּמָה, בְּחֻלִּין שֶׁנַּעֲשׂוּ לְטָהֳרַת תְּרוּמָה:

Mishnah Taharos 2:3: Non-sacred food of a first degree [level of impurity] is impure and can render others impure. That of a second degree, is invalid [literally: renders invalid], but does not render impure. And [non-sacred food] of a third degree can be eaten in a soup of demai [non-sacred foods into which some amount of terumah has been mixed].

הָרִאשׁוֹן שֶׁבַּחֻלִּין, טָמֵא וּמְטַמֵּא. הַשֵּׁנִי פּוֹסֵל וְלֹא מְטַמֵּא. וְהַשְּׁלִישִׁי נֶאֱכָל בִּנְזִיד הַדָּמַע: