Hard Riddles for Adults

At a border I may be crossed; in a queue I may be joined; in a script I may be delivered. Same word, three places. What am I?

The moment I am told, I still exist, but I no longer belong to one person. Add more keepers and I become harder to keep. What am I?

I tell time by copying the sun's refusal to stand still; indoors I am useless, and at noon I almost disappear. What am I?

Move me one place in an invoice and ten pounds becomes a hundred; I look tiny, but I can empty a budget. What am I?

Evidence can open me, fear can close me, and one conversation can change me without touching me. What am I?

I am not written on a CV; comfort may hide me, pressure reveals me, and repeated choices build me slowly. What am I?

A detective may reach me without taking a step, and one false clue can send me in the wrong direction. What am I?

A coin is a circle on the table, an oval from the side, and almost a line at eye level. What changed?

Project managers like me broken into tasks; ignored, I grow costlier; examined, I reveal the next step. What am I?

A camera needs me before the picture is sharp; a meeting loses me when every phone starts buzzing. What am I?

A lawyer builds me with facts, doubt weakens me, and proof can make me strong again. What am I?

I begin with two premises and end with a conclusion; if my middle term fails, so do I. What am I?

Scientists trust me only after trying to prove me wrong; assume me without testing and I am just a guess. What am I?

You can count along me, divide me, make me negative, and still never reach my final member. What am I?

Eight is correct after five plus three, wrong after five times three, and meaningless on a blank page. What am I?

I find cracks before publication, improve an argument by pressing its weak points, and work best when the attack is fair. What am I?

Write me in a diary and I am ahead of you; wake up inside me and everyone calls me today. What am I?

Ten seconds before midnight I make a room loud; ten seconds before an exam I make it silent. Same numbers, different feeling. What am I?

I arrive slowly through kept promises, leave quickly after one public lie, and often enter the room before you do. What am I?

A violin string needs enough of me to sing; a room after an argument can have too much of me, even in silence. What am I?

Court records, photographs and scars can show me. Apologies may change my meaning, but not my events. What am I?