Is it permissible for a younger person to bow to an older person when greeting them?

 

Shirk in respect confuses me a lot! There is a tradition in my relatives that they bow a little in front of their elders, their elders keep their hand on their heads out of love, however, the young ones dont bow as much as one bows in Ruku. I have seen almost all people.

Praise be to Allaah.

It is not permissible to bow when meeting someone, whether he
is a scholar or anyone else. 

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him)
said: 

With regard to bowing when greeting someone, it is forbidden
as is narrated in al-Tirmidhi from the Prophet (blessings and peace of Allah
be upon him); they asked him about a man who meets his brother, can he bow
to him? He said: “No.” And it is not permissible to bow or prostrate to
anyone except Allah, may He be glorified and exalted, even though that may
have been a form of greeting in other religions, as in the story of Yoosuf –
“…and they fell down before him prostrate. And
he said: ‘O my father! This is the interpretation of my dream aforetime!’”
[Yoosuf 12:100]. But in our religion it is not acceptable to bow or
prostrate to anyone except Allah; in fact it is also forbidden to stand as
the non-Arabs stand before one another, so how about bowing and prostrating?
Similarly, a partial bow is also included in this prohibition.

End quote from Majmoo‘ al-Fataawa, 1/377 

And he said: 

With regard to lowering the head when meeting prominent
figures such as shaykhs and so on, or kissing the ground and so on, these
are things concerning which there is no difference of opinion among the
imams that they are forbidden. In fact merely inclining the back to anyone
other than Allah, may He be glorified and exalted, is forbidden. In
al-Musnad and elsewhere it is narrated that when Mu‘aadh ibn Jabal came
back from Syria, he prostrated to the Prophet (blessings and peace of Allah
be upon him), who said: “What is this, O Mu‘aadh?” He said: O Messenger of
Allah, I saw them in Syria prostrating to their bishops and patriarchs, and
they narrated that from their Prophets. He said: “They are lying, O Mu‘aadh;
if I were to instruct anyone to prostrate to anyone else, I would have
instructed a woman to prostrate to her husband because of the greatness of
his rights over her. O Mu‘aadh, do you think that if you were to pass my
grave you would prostrate?” He said: No. He said: “Do not do that,” or words
to that effect. 

To sum up: standing, sitting, bowing and prostrating are due
only to the only One Who is deserving of worship, the Creator of the heavens
and the earth; with regard to that which is due only to Allah, no one should
have any share in it; this also applies to swearing by anything other than
Allah, may He be glorified and exalted.

End quote from Majmoo‘ al-Fataawa, 27/92, 93 

The scholars of the Standing Committee said: 

It is not permissible to bow when greeting or to take off
one’s shoes for him. 

And they said: 

It is not permissible to bow when greeting a Muslim or a
kaafir, whether with the upper part of the body or the head, because bowing
is a form of worship, and worship can only be for Allah alone. 

Shaykh ‘Abd al-‘Azeez ibn Baaz, Shaykh ‘Abd al-Razzaaq
‘Afeefi, Shaykh ‘Abd-Allah ibn Ghadyaan, Shaykh ‘Abd-Allah ibn Qa‘ood 

Fataawa al-Lajnah al-Daa’imah,
1/233, 234 

And Allah knows best.