Thread in Chinese / Japanese...

誰言寸草心報得三春暉 is the last line of a famous poem. It is perceived as a tribute or ode to your parents or mother from a child or children that have left home.

The poem was written by Meng Jiao during the Tang Dynasty (about 1200 years ago). The Chinese title is “You Zi Yin” which means “The Traveler's Recite.”

The last line as shown here speaks of the generous and warm spring sunlight which gives the grass far beyond what the little grass can could ever give back (except perhaps by showing its lovely green leaves and flourishing). The metaphor is that the sun is your mother or parents, and you are the grass. Your parents raise you and give you all the love and care you need to prepare you for the world. A debt that you can never repay, nor is repayment expected.

The first part of the poem (not written in the characters to the left) suggests that the thread in a loving mother's hands is the shirt of her traveling offspring. Vigorously sewing while wishing them to come back sooner than they left.
...This part is really hard to translate into English that makes any sense but maybe you get the idea. We are talking about a poem that is so old that many Chinese people would have trouble reading it (as if it was the King James Version of Chinese).

This literally translates as “the red string” or “the red thread” in Japanese, but the real meaning is much deeper...

In Japanese culture, it's believed that fate, destiny, or karma joins lovers by an unseen string, tied around one little finger of each. 赤い糸 is how soul mates find and are drawn to each other.

The Japanese concept of the red thread of fate, by most estimations, comes from Chinese folklore, where it's known as 姻緣紅線. The only difference is that in China, the celestial red thread is tied around the ankles of the lovers (versus what is usually represented as the pinky finger in Japan).

姻緣紅線 is the legendary red string of destiny that binds all soul mates or lovers together.

In ancient Chinese culture, a mythological matchmaker named 月老 (Yuè Lǎo) was the controller of the fate that led lovers to meet. He did this by tying a celestial red string to the ankle of each person. Sometime during their life, they will meet and marry as fate dictates.

While the origin of the red string comes from China, it has spread to other parts of Asia (such as Japan, where it's known as 赤い糸).

絲 is the simplest way to write silk in Chinese, Japanese Kanji, and old Korean Hanja.

This can also mean thread, and it is used as parts of words like “silk fabric” or “silk scarf.”

In Japanese, this can be the surname Ito.

絲 is used far more in Chinese for silk (silk comes from China) than in Japanese.

有緣千里來相會 means that fate or destiny has caused us to meet from a thousand miles away.

The 有緣 part suggests something that is connected as if by a thread due to fate, destiny, or karma.

This romantic phrase is seen in Chinese greeting cards. It relays the idea that your love was meant to be and that you were destined to meet (regardless of what distance or obstacles might have made such a meeting unlikely).

吾道一以貫之 is a phrase from the Analects of Confucius that translates as “My Way has one thread that runs through it.”

Other translations include:
My Way is penetrated by a single thread.
There is one single thread binding my Way together.
My Way is run through with a unifying thread.
My Way is Consistent.
And sometimes poetic license is taken, and it is translated as:
My Way is the only one; I'll treasure it and stick to it with humility until the end.

After this was said, some 2500+ years ago, another disciple of Confucius clarified the meaning by stating, “Our master's Way is to be loyal and have a sense of reciprocity.”

In Japanese, this is purported to be romanized as “Waga michi ichi wo motte kore wo tsuranuku,” though some will argue the true pronunciation.

Note: Sometimes written 吾道以一貫之 instead of 吾道一以貫之 with no difference in meaning.

This is Seichusen, the Japanese martial arts concept meaning “right/correct middle/center line/thread.”