Before considering the role that Buddhist and Shinto rituals have in Japan, it is first worthwhile distinguishing between them. First, 神道 (Shinto) is the honoring of 神 (often respectfully referred to as 神様) spirits that represent the way the earthly realm interacts with the spiritual one. This worship takes place at a 神社 (Shinto shrine).
So far so simple. However, things get a little more complicated with the people and entities involved in 仏教 (Buddhist) philosophy. Buddhism has two key figures called the 仏 and 釈迦. The word 釈迦, or Buddha, refers to the creator of Buddhism, Gautama Siddhartha himself. On the other hand, 仏 refers to someone who has obtained enlightenment, but not necessarily the original Buddha himself.
The statues of the Buddha Kannon, for example, are often represented as being female — so obviously she isn’t the original (male) Buddha. She would therefore be 仏, but obviously not 釈迦.
Because anyone can in theory be 仏, assuming they are willing to dedicate themselves to Buddhist virtues, you will occasionally hear the term being used to compliment someone for their saintly nature 仏のような人だ, for example, is a way to say that someone is so patient they are almost Buddha-like in nature.
Naturally, in the real world, not everyone is suitable for the extreme discipline required to become a Buddhistmonk. As a result, an expression 三日坊主 was created for these people. This comes from the stories of young monks (坊主) who would shave their heads only to discover that the harsh discipline and restrictive rules of the temples were too much for them and would usually quit — after three days (三日). Over time, this has come to mean someone who gives up on things too quickly.
The twin religions of Buddhism and Shinto have become such a part of the culture that its way of thinking has bled into the language itself.
Of course, even the most devout of people can only be pushed so far by their unmotivated 坊主. While the Buddha himself might disagree, the saying 仏の顔も三度(まで) is a tongue-in-cheek way of saying that even a Buddha’s face (仏の顔) can only take insults three times (三度) before cracking. It translates roughly as: “Even the patience of a saint has limits.”
The old joke that “the wisest is the one who does not know” could almost be a Japanese piece of wisdom. Similar to the English aphorism that “ignorance is bliss,” the Japanese say that not knowing makes one as peaceful as a Buddha 知らぬが仏. Or, as a Shinto practitioner would have it: Don’t worry because 神のみぞ知る (“God only knows”).
If the ignorance gets too much and you are forced to face hardship, Japan has a bleak saying that 苦しいときの神頼み is turning to the Kami at times of troubles. It is often said bitingly to mean that one only turns to the gods when things are at their darkest.
While many Japanese will tell you that they are not religious, it is often very difficult to separate Japanese culture from its religious roots. The twin religions of Buddhism and Shinto have become such a part of the culture that its way of thinking has bled into the language itself. By internalizing some of these words, it offers learners a way to express themselves about these matters. They can also gain a greater insight into the complicated way religious thought informs even the relatively secular and modern face of Japan.