In Hebrew: 'Not Necessarily'

לָאו דַּוְקָא, לֹא בְּהֶכְרֵחַ

For example:

עִיר בְּשֵׁם יְרוּשָׁלַיִם לָאו דַּוְקָא נִמְצֵאת בְּיִשְׂרָאֵל. A city by the name of Jerusalem isn't necessarily located in Israel.(see an entry on דווקא)

or

עִיר בְּשֵׁם יְרוּשָׁלַיִם לֹא בְּהֶכְרֵחַ נִמְצֵאת בְּיִשְׂרָאֵל. (same meaning)

(There are cities called Jerusalem in the United States and probably other places as well.)

To say that something is necessary logically, use the word הֶכְרֵחִי. Otherwise, use נָחוּץ  to mean necessary, as in:

נָחוּץ לְהָבִיא בִּגּוּד חָם לַטִּיּוּל. (It's) necessary to bring warm clothing for the trip. .

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