In Mesilas Yesharim, the Ramchal (R’ Moshe Chaim Luzato) writes of three kinds of yir’ah (fear / awe / awareness of magnitude).

1- Yir’as ha’onesh: fear of punishment. This is the lowest of the three. However, since even fear of punishment is a motivator, even yir’as ha’onesh is viewed positively.

R’ Shlomo Wolbe zt”l writes that today, we’ve lost that motivating quality. Punishment invokes more thoughts of rebellion than of compliance. He therefore bans corporal punishment of children, and also plays down the role of yir’as ha’onesh a generation raised on democracy, rights, and personal freedoms.

2- Yir’as Shamayim: fear of [the One in] heaven

This is the lofty goal. It, in turn, comes in two flavors:

2a- Yir’as hacheit: fear of sin. This is distinct from the fear of punishment; it’s fear of the sin itself, of the possibility of erring. Mesilas Yesharim continues that when a traditional source speaks of “yir’ah” without specification, it means yir’as hacheit (fear of the sin [itself]).

Which would mean that it’s fair to assume this is the kind of yir’as shamayim is the one R’ Avraham Elya Kaplan described in Be’ikvos haYir’ah (translation from an article by R’ Yosef Gavriel Bechhofer).

…But one who has not traversed the actual pathway of illumination [that of the prophets and the sages],he who stands opposite the rays of light, at some distance, possesses little understanding of this term [yir’ah]. It would be better had he never known this term, and was now learning it for the first time. But this is his problem: He knows it, but does not know it properly. He possesses a dangerous translation of the entire concept, and cannot avoid its negative ramifications. For example, when we mention yir’ah to this person he can only translate it thus: Bent head, wrinkled brow, glazed eyes, hunched back, trembling left hand, right hand clapping al cheit, knocking thighs, failing knees, stumbling heels. And he does not know that this translation is heretical for the one who knows what yir’ah is and what it means, the source from which it flows, and from whence it comes… There are times that demand tears and eulogies… It is necessary then to stoop like rushes and take up sackcloth and ashes. Times come upon the world when our sins require these. Such, however, is not Yir’as Hashem, not it and not even part of it. It is not yir’ah’s essence, but only preparation for it…Yir’ah is not anguish, not pain, not bitter anxiety. To what may yir’ah be likened? To the tremor of fear which a father feels when his beloved young son rides his shoulders as he dances with him and rejoices before him, taking care that he not fall off. Here there is joy that is incomparable, pleasure that is incomparable. And the fear tied up with them is pleasant too. It does not impede the freedom of dance… It passes through them like a spinal column that straightens and strengthens. And it envelops them like a modest frame that lends grace and pleasantness… It is clear to the father that his son is riding securely upon him and will not fall back, for he constantly remembers him, not for a moment does he forget him. His son’s every movement, even the smallest, he feels, and he ensures that his son will not sway from his place, nor incline sideways – his heart is, therefore, sure, and he dances and rejoices. If a person is sure that the “bundle” of his life’s meaning is safely held high by the shoulders of his awareness, he knows that this bundle will not fall backwards, he will not forget it for a moment, he will remember it constantly, with yir’ah he will safe keep it. If every moment he checks it – then his heart is confident, and he dances and rejoices…

When the Torah was given to Israel solemnity and joy came down bundled together. They are fused together and cannot be separated. That is the secret of “gil be’re’ada” (joy in trembling) mentioned in Tehillim. Dance and judgment, song and law became partners with each other… Indeed, this is the balance… A rod of noble yir’ah passes through the rings of joy… {It is clear from the original Hebrew that this is a reference to the rods that held the boards together to make the walls of the Tabernacle. -mi} [It is] the inner rod embedded deep in an individual’s soul that connects end to end, it links complete joy in this world (eating, drinking and gift giving) to that which is beyond this world (remembering the [inevitable] day of death) to graft one upon the other so to produce eternal fruit.

A Swedish wise man, when once discussing sanctity, said: “The sanctity of an individual proves that he who possesses it has a direct relationship with the strongest source of existence.” In my opinion, in the conception of Judaism this is a definition of yir’ah (but sanctity – kedusha – is loftier still, we have a different idea of it, but this is not the place to define it). What is yir’ah? It is the broad jump over the vast gap between myself and my Creator… It is a mitzvah to separate – to separate from smallness! Fly over barriers! And from there quest Him, for there you will find Him…

It is a kind of fear of heaven that one is worried about letting G-d down, about doing something that would ruin the relationship.

The Maharal (Nesivas Olam, Nesiv Yir’as Hashem chapter 1) writes that “yir’as hacheit” (fear of the sin itself, which the Ramchal called the default definition) comes from a love of Hashem. When you love Someone, you give great importance to not disappointing Him.

2b- Yir’as haRomemus: fear of the Grandeur [of G-d]

Note that as the Ramchal progresses, the translation for yir’ah as “fear” becomes steadily less compelling, and that of awe, or acting with awareness of the magnitude of what one is engaging in, seem more appropriate. And actually, awareness of magnitude brings more weight to the event. It’s the difference between the joy of dancing at a siyum and that of dancing at a daughter’s wedding. Because the wedding is so momentous, the joy is that much more intense. To return to R’ Avraham Elya Kaplan’s metaphor, the depth of my love for my son adds to the joy of dancing with him. Without the yir’ah, the awareness of what a big thing it is to put one’s son atop one’s shoulders, the joy wouldn’t be there.

I don’t think that the more primary definition of “yir’ah” could possibly be “fear”. The Torah writes “Your mother and your father tirah — you should feel yir’ah.” Living in fear of one’s parents is unhealthy, and obviously not the Torah’s intent. Rather, I believe that “yir’ah”‘s primary meaning is that of the awareness, and from notion of awareness one can speak of awareness of the magnitude of possible upcoming bad consequences and gets the derived meaning of “fear”.

Later in the essay, R’ AE Kaplan writes:

Indeed, this is the direct relationship. Indeed, this is the true vision that we call yir’ah… And this, therefore, is the reason that we dwell so much on fear of punishment (“yir’as ha’onesh”). This is also vision – seeing things as they really are… One who refuses to see his future shortchanges only himself. Only if he sees (re’iyah) will he fear (yir’ah), and only if he fears will he repent… And from here we proceed to the fear [awe] of loftiness (“yir’as haromemus”) – that is the vision [the perception] of loftiness. From here – “The maid servant at the Red Sea saw loftier visions than the Prophet Yechezkel.” From here comes the direct view, across all the dividers, to the source of existence. This is an unceasing inner gaze toward the matter that is one’s responsibility [the bundle of his life’s meaning] (that he must safeguard lest it fall…). The gaze is one that leads to remembrance, remembrance that leads to care, care that leads to confidence, confidence that leads to strength (“oz”) – an inner, bold, uplifting, strength (“Hashem oz li’amo yiten…”) and a strength that leads to peace (“shalom”) and wholeness, internally and externally, in thought and in deed (“… Hashem yivareich es amo ba’shalom”). Indeed, This is the wisdom of life: “Reishis chochma yir’as Hashem.” A fear that is vision. “And remember” – “And see” – “Shivisi Hashem l’negdi tamid…

Even yir’as ha’onesh has an important role. One who avoids it is avoiding dealing with things as they truly are. Facing reality, allowing oneself to experience (re’iyah) G-d’s interaction in our lives — both positive and not so — leads to being overawed by Him (yir’ah, i.e. “yir’as Shamayim veyir’as hacheit”). That is the yir’ah we are being asked to develop alongside ahavah in our relationship with Hashem. True yir’as shamayim, rather than being about quaking in one’s boots, debilitated, leads one to joy, song and action. And in fact, adds to the ahavah, the Love of G-d. By facing a glimmer of the Greatness of the Beloved, we come to treasure that love, and love Him all the more. “Az yashir — And then he will sing…”