How to Say "Older Sister" in Thai

พี่สาว

pîi-sǎao/pʰiː˥˩.saːw˩˩˦/

The Thai word for "older sister" is พี่สาว (pîi-sǎao).

The term พี่สาว is suitable for addressing a blood-related older sister or an unfamiliar person who is older than you.

Meaning: single-word translations (noun)

What does it mean word for word?

The word is composed of พี่ (pîi), meaning older sibling and สาว (sǎao), meaning young woman or female.

While พี่สาว refers specifically to an older sister, พี่ชาย is the term used for an older brother.

The two-syllable romanization is pîi-sǎao.

Calling someone พี่ when they are actually younger than you is a common social strategy used by sellers or service workers to make the customer feel more senior and respected.
The term พี่สาว is a cognate with the phrase Pi Sau in the Ahom language, which was used by the founders of the Ahom Kingdom in present-day Assam, India.
While 'sister' in English is often just a title, using พี่สาว in Thai can change the entire power dynamic of a conversation by establishing a hierarchical social order.

พี่สาวของผมสวย
My older sister is beautiful.
This sentence is useful for practicing how to describe the beauty of a พี่สาว.
Tatoeba #1750062 by Vortarulo, translation #3075823 by AkuNeko
พี่สาวของฉันอยู่ที่กรุงเทพฯ
phi sao khong chan yu thi bangkok
My older sister is in Bangkok.
เขามีพี่สาวสองคน
khao mi phi sao song khon
He has two older sisters.

Teerapat and Nicha are talking about family members at a cafe.

ธีรภัทร Theeraphat

ณิชามีพี่สาวไหม
nicha mi phi sao mai
Does Nicha have an older sister?
ณิชา Nicha

มีค่ะ พี่สาวของฉันเป็นหมอ
mi kha phi sao khong chan pen mor
Yes, I do. My older sister is a doctor.
ธีรภัทร Theeraphat

เก่งมากเลยครับ
keng mak loei khrap
That is very impressive.
ณิชา Nicha

ขอบคุณค่ะ
khop khun kha
Thank you.

Sources

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