Zt"l

Among the honorifics in Judaism, there are several traditional honorifics for the dead which are used when naming and speaking of the deceased. Different honorifics might be applied depending on the particular status of the deceased. These honorifics are frequently found on gravestones, on memorial walls inside the sanctuary of synagogues, in speeches, and in writing such as in obituaries.

In writing, it is most common to use the name followed by an abbreviation of an honorific either in Hebrew or English. For examples, see chart.

The following chart shows different honorifics used, along with their abbreviation in Hebrew and English, their translation, the masculine and feminine forms, the type of person which the honorific is applied to, and examples.

Some honorifics may be used for any individual. These honorifics are generally not used for rabbis or other special persons, since the specific honorifics for those people are used instead, as a sign of honor and respect. See below.

The most common honorific is "of blessed memory," and the Hebrew transliteration is "zikhrono livrakha" (m.) / "zikhronah livrakha" (f.) (Hebrew: (f.) "זיכרונה לברכה" \ (m.) "זיכרונו לברכה"). It is often abbreviated in English both as OBM and as “Z"L” The Hebrew abbreviation is "ז״ל."

An alternative honorific is "Peace be upon him/her." The Hebrew version is "alav ha-shalom" (m.) / "aleha ha-shalom" (f.) (Hebrew: (m.) "עליו השלום" / (f.) "עליה השלום"). It is abbreviated in English as “A"H.” The Hebrew abbreviation is "ע״ה."

This phrase is the same as the Islamic honorific "peace be upon him" (which is used for all prophets of Islam). However, unlike in Islamic usage, the English abbreviation "PBUH" is not commonly used for the Jewish honorific.

The above two may be used interchangeably; however "of blessed memory" is the most common.

This honorific "May Hashem avenge his/her blood" is used for an individual who perished as a result of anti-semitism, for example pogroms or the Holocaust. The Hebrew version is "Hashem yinkom damo" (m.) / "Hashem yinkom dama" (f.) and in the Hebrew: (f.) " השם ינקום דמה" \ (m.) "השם ינקום דמו." The English abbreviation is “HY"D” and in Hebrew "הי״ד."

...
Wikipedia