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If you've been minimally affiliated with any Judeo-Christian institution... ever, you're familiar with the word אָמֵן (ah-MEN) - amen. The three-letter root of the word makes up the entire word. Its core meaning is trust.
Thus the word for reliable is אָמִין (ah-MEEN), or אָמִינָה (ah-mee-NAH), when speaking of a female or a feminine object.
For example, זֶה רֶכֶב אָמִין (zeh REH-khev ah-MEEN) - This is a reliable vehicle.